Positive photosensitive composition

ABSTRACT

A positive photosensitive composition comprises a compound capable of generating a specified sulfonic acid upon irradiation with one of an actinic ray and radiation and (B) a resin capable of decomposing under the action of an acid to increase the solubility in an alkali developer.

This application is a divisional of application Ser. No. 10/866,054,filed Jun. 14, 2004, which is a divisional of application Ser. No.09/978,103, filed Oct. 17, 2001 (now U.S. Pat. No. 6,749,987), theentire disclosures of both of which are hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to a positive photosensitive compositionused in the manufacturing process of a lithographic printing plate or asemiconductor such as IC, in production of a circuit board for a liquidcrystal device or a thermal head, and in the process of the otherphotofabrications.

BACKGROUND OF THE INVENTION

Various photosensitive compositions have been used in the manufacturingprocess of a lithographic printing plate, a semiconductor such as IC, inproduction of circuit boards for a liquid crystal device and a thermalhead, and in the process of photofabrication for other devices. As thephotosensitive compositions for these uses, photoresist photosensitivecompositions are generally utilized, and they are broadly classifiedinto two groups, namely the group of positive photoresist compositionsand the group of negative ones.

Representatives of such positive photoresist compositions are chemicalamplification resist compositions as disclosed in U.S. Pat. No.4,491,628 and European Patent No. 249,139.

Chemical amplification positive resist compositions are materials forforming patterns on substrates. More specifically, these compositionsgenerate acids by irradiation with actinic rays, such as far ultravioletrays, and undergo reaction utilizing these acids as a catalyst. Thisreaction causes a difference in solubilities in a developer between theareas unirradiated and irradiated with the actinic rays, therebyenabling pattern formation.

Examples of such chemical amplification positive resist compositionsinclude the combination of a compound capable of generating an acid byphotolysis (hereinafter abbreviated as a photo-acid generator) and anacetal or O,N-acetal compound (JP-A-48-89003, the term “JP-A” as usedherein means an “unexamined published Japanese Patent application), thecombination of a photo-acid generator and an orthoester or amidoacetalcompound (JP-A-51-120714), the combination of a photo-acid generator anda polymer having acetal or ketal groups on the main chain(JP-A-53-133429), the combination of a photo-acid generator and an enolether compound (JP-A-55-12995), the combination of a photo-acidgenerator and an N-acylaminocarbonic acid compound (JP-A-55-126236), thecombination of a photo-acid generator and a polymer having orthoestergroups on the main chain (JP-A-56-17345), the combination of aphoto-acid generator and a tertiary alkyl ester compound (JP-A-60-3625),the combination of a photo-acid generator and a silyl ester compound(JP-A-60-10247), and the combination of a photo-acid generator and asilyl ether compound (JP-A-60-121446). These compositions have highphotosensitivity since the their quantum yields are each greater than 1in principle.

As examples of a system which is stable upon storage at room temperaturebut decomposed by heating in the presence of an acid to becomealkali-soluble, mention may be made of the systems obtained by combiningtertiary or secondary carbon-containing (such as t-butyl or2-cyclohexenyl) ester or carboxylic acid ester compounds and compoundscapable of generating acids by exposure as described in JP-A-59-45439,JP-A-60-3625, JP-A-62-229242, JP-A-63-27829, JP-A-63-36240,JP-A-63-250642, Polym. Eng. Sce., vol. 23, p. 1012 (1983), ACS. Sym.,vol. 242, p. 11 (1984), Semiconductor World, the November issue in 1987,p. 91, Macromolecules, vol. 21, p. 1475 (1988), and SPIE, vol. 920, p.42 (1988). These systems also have high photosensitivity, and show poorabsorption in the far ultraviolet region. Therefore, they can beeffective in enabling the use of a light source with shorter wavelengthssuitable for submicron photolithography.

The chemical-amplification positive resist compositions as mentionedabove are broadly classified into two groups. One group includesthree-component systems which are each constituted of an alkali-solubleresin, a compound capable of generating an acid upon exposure toradiation (photo-acid generator) and a compound having anacid-decomposable group and inhibiting dissolution of an alkali-solubleresin. The other group includes two-component systems which are eachconstituted of a resin having groups capable of being decomposed byreaction with an acid to become alkali-soluble and a photo-acidgenerator.

In such two-component or three-component positive resist of chemicalamplification type, resist patterns are formed by development afterthermal treatment in the presence of an acid generated from a photo-acidgenerator by exposure.

As mentioned above, such chemical amplification positive resistcompositions can be systems suitable for a light source with shorterwavelengths enabling submicron photolithography. However, furtherimprovements in resolution and process latitude, including exposuremargin or focus depth, have been required for them.

In such systems, compounds capable of generatingtrifluoromethanesulfonic acid, such as triphenylsulfoniumtrifluoromethanesulfonate, and compounds capable of generatinglonger-chain fluoroalkylsulfonic acids are used as photo-acidgenerators.

Further, compounds capable of perfluoroalkanesulfonic acids, such astriphenylsulfonium triflate and bis(t-butylphenyl)iodoniumperfluorobutanesulfonate, are also well known as photo-acid generators.A compound capable of generating a perfluorobutanesulfonic acid isdescribed in WO 00/08525, JP-A-09-12537, JP-A-2000-275845 and EP1041442A.

In general, perfluoroalkyl compounds have high hydrophobicity, so theyare used for water-repellent coating on clothes. Therefore, the resistusing an acid generator capable of generating a perfluoroalkylsulfonicacid upon irradiation with actinic rays has a low affinity for aqueousdevelopers, and so it suffers from a sensitivity drop and scumdevelopment due to degradation in developability.

Further, the arts mentioned above cannot satisfactorily meet the currentneeds for photolithography and have room for improvements in resolutionand process latitude, including exposure margin and focus depth.

SUMMARY OF THE INVENTION

Therefore, an object of the invention is to provide a positivephotosensitive composition which can ensure high resolution and improvedexposure margin in photolithography utilizing a light source forshort-wavelength exposure enabling super minute patterning and achemical-amplification positive resist.

Another object of the invention is to provide a positive resistcomposition enabling reduction in scum and improvement in processlatitude, including exposure margin and focus depth.

The following positive resist compositions are provided as embodimentsof the invention, and thereby the aforementioned objects can beattained.

(1) A positive photosensitive composition comprising:

(A) a compound capable of generating a sulfonic acid represented byformula (X) below upon irradiation with one of an actinic ray andradiation; and

(B) a resin capable of decomposing under the action of an acid toincrease the solubility in an alkali developer:

wherein R_(1a) to R_(13a) groups each represents a hydrogen atom, analkyl group, a haloalkyl group, a halogen atom or a hydroxyl group; A₁and A₂, which are the same or different, each represents a single bondor a hetero atom-containing divalent linkage group, provided that, wheneach of A₁ and A₂ is single bond, all of the R_(1a) to R_(13a) groups donot simultaneously represent a fluorine atom and all of the R_(1a) toR_(13a) groups do not simultaneously represent a hydrogen atom; m₁ tom₅, which are the same or different, each represents an integer of 0 to12; and p represents an integer of 0 to 4.

(2). The positive photosensitive composition as described in item (1),wherein the sulfonic acid represented by formula (X) comprises acompound represented by formula (X′)

wherein R_(1a) to R_(13a) groups each represents a hydrogen atom, analkyl group, a haloalkyl group, a halogen atom or a hydroxyl group; A₁and A₂, which are the same or different, each represents a single bondor a hetero atom-containing divalent linkage group, provided that, wheneach of A₁ and A₂ is single bond, all of the R_(1a) to R_(13a) groups donot simultaneously represent a fluorine atom and all of the R_(1a) toR_(13a) groups do not simultaneously represent a hydrogen atom; mrepresents an integer of 0 to 12; n represents an integer of 0 to 12;and q represents an integer of 1 to 3.

(3). The positive photosensitive composition as described in item (1),which further comprises (C) a dissolution-inhibiting compound having amolecular weight of not more than 3,000 which contains anacid-decomposable group and can increase the solubility in an alkalideveloper by the action of an acid.

(4). The positive photosensitive composition as described in item (1),wherein the resin (B) contains a lactone structure.

(5). The positive photosensitive composition as described in item (1),wherein the compound (A) comprises at least one of an iodonium salt ofthe sulfonic acid represented by formula (X) and sulfonium salt of thesulfonic acid represented by formula (X).

(6). A positive photosensitive composition as described in item (1),wherein the compound (A) comprises at least one compound selected fromcompounds represented by formulae (I) to (III):

wherein R₁ to R₃₇ groups, which are the same or different, eachrepresents a hydrogen atom, a straight-chain or branched alkyl grouphaving 1 to 4 carbon atoms, a cycloalkyl group having 3 to 8 carbonatoms, a alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, ahalogen atom, or an —S—R₃₈ group; R₃₈ represents a straight-chain orbranched alkyl group having 1 to 12 carbon atoms, a cycloalkyl grouphaving 3 to 8 carbon atoms, or an aryl group having 6 to 14 carbonatoms; X⁻ represents an anion of the sulfonic acid represented byformula (X) described above.

(7). The positive photosensitive composition as described in item (1),wherein at least one of the R_(1a) to R_(13a) groups in formula (X)represents a fluorine atom.

(8). The positive photosensitive composition as described in item (1),wherein the sulfonic acid represented by formula (X) comprisesCF₃CF₂—O—CF₂CF₂SO₃H.

(9). The positive photosensitive composition as described in item (1),wherein the resin (B) contains at least one of a monocyclic alicyclicstructure and polycyclic alicyclic structure.

(10). A positive photosensitive composition comprising:

(A) a compound capable of generating a sulfonic acid represented byformula (X) below upon irradiation with one of an actinic ray andradiation;

(C) a dissolution-inhibiting compound having a molecular weight of notmore than 3,000 which contains an acid-decomposable group and canincrease the solubility in an alkali developer by the action of an acid;and

(D) a resin insoluble in water and soluble in an alkali developer;

wherein R_(1a) to R_(13a) groups each represents a hydrogen atom, analkyl group, a haloalkyl group, a halogen atom or a hydroxyl group; A₁and A₂, which are the same or different, each represents a single bondor a hetero atom-containing divalent linkage group, provided that, wheneach of A₁ and A₂ is single bond, all of the R_(1a) to R_(13a) groups donot simultaneously represent a fluorine atom and all of the R_(1a) toR_(13a) groups do not simultaneously represent a hydrogen atom; m₁ tom₅, which are the same or different, each represents an integer of 0 to12; and p represents an integer of 0 to 4.

(11). The positive photosensitive composition as described in item (10),wherein the sulfonic acid represented by formula (X) comprises acompound represented by formula (X′)

wherein R_(1a) to R_(13a) groups each represents a hydrogen atom, analkyl group, a haloalkyl group, a halogen atom or a hydroxyl group; A₁and A₂, which are the same or different, each represents a single bondor a heteroatom-containing divalent linkage group, provided that, wheneach of A₁ and A₂ is single bond, all of the R_(1a) to R_(13a) groups donot simultaneously represent a fluorine atom and all of the R_(1a) toR_(13a) groups do not simultaneously represent a hydrogen atom; mrepresents an integer of 0 to 12; n represents an integer of 0 to 12;and q represents an integer of 1 to 3.

(12). The positive photosensitive composition as described in item (10),wherein the compound (A) comprises at least one of an iodonium salt ofthe sulfonic acid represented by formula (X) and sulfonium salt of thesulfonic acid represented by formula (X).

(13). The positive photosensitive composition as described in item (10),wherein the compound (A) comprises at least one compound selected fromcompounds represented by formulae (I) to (III):

wherein R₁ to R₃₇ groups, which are the same or different, eachrepresents a hydrogen atom, a straight-chain or branched alkyl grouphaving 1 to 4 carbon atoms, a cycloalkyl group having 3 to 8 carbonatoms, a alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, ahalogen atom, or an —S—R₃₈ group; R₃₈ represents a straight-chain orbranched alkyl group having 1 to 12 carbon atoms, a cycloalkyl grouphaving 3 to 8 carbon atoms, or an aryl group having 6 to 14 carbonatoms; X⁻ represents an anion of the sulfonic acid represented byformula (X) described above.

(14). The positive photosensitive composition as described in item (10),wherein at least one of the R_(1a) to R_(13a) groups in formula (X)represents a fluorine atom.

(15). The positive photosensitive composition as described in item (10),wherein the sulfonic acid represented by formula (X) comprisesCF₃CF₂—O—CF₂CF₂SO₃H.

(16) The positive photosensitive composition as described in item (10),wherein the resin (D) contains at least one of a monocyclic alicyclicstructure and polycyclic alicyclic structure.

(17). An iodonium or sulfonium salt compound represented by formulae (I)to (III):

wherein R₁ to R₃₇ groups, which are the same or different, eachrepresents a hydrogen atom, a straight-chain or branched alkyl grouphaving 1 to 4 carbon atoms, a cycloalkyl group having 3 to 8 carbonatoms, a alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, ahalogen atom, or an —S—R₃₈ group; R₃₈ represents a straight-chain orbranched alkyl group having 1 to 12 carbon atoms, a cycloalkyl grouphaving 3 to 8 carbon atoms, or an aryl group having 6 to 14 carbonatoms; X⁻ represents an anion of a sulfonic acid represented by formula(X);

wherein R_(1a) to R_(13a) groups each represents a hydrogen atom, analkyl group, a haloalkyl group, a halogen atom or a hydroxyl group; A₁and A₂, which are the same or different, each represents a single bondor a hetero atom-containing divalent linkage group, provided that, wheneach of A₁ and A₂ is single bond, all of the R_(1a) to R_(13a) groups donot simultaneously represent a fluorine atom and all of the R_(1a) toR_(13a) groups do not simultaneously represent a hydrogen atom; m₁ tom₅, which are the same or different, each represents an integer of 0 to12; and p represents an integer of 0 to 4.

(18). The iodonium or sulfonium salt compound as described in item (17),wherein the sulfonic acid represented by formula (X) is a compoundrepresented by formula (X′):

wherein R_(1a) to R_(13a) groups each represents a hydrogen atom, analkyl group, a haloalkyl group, a halogen atom or a hydroxyl group; A₁and A₂, which are the same or different, each represents a single bondor a hetero atom-containing divalent linkage group, provided that, wheneach of A₁ and A₂ is single bond, all of the R_(1a) to R_(13a) groups donot simultaneously represent a fluorine atom and all of the R_(1a) toR_(13a) groups do not simultaneously represent a hydrogen atom; mrepresents an integer of 0 to 12; n represents an integer of 0 to 12;and q represents an integer of 1 to 3.

Additionally, the present photosensitive compositions can deliverexcellent resist performances even when electron beams are used asenergy beams for irradiation. The irradiation with electron beams has aproblem that the incident beams interact with atomic nuclei andelectrons of ingredients in resist because of their electric charges, sothat when electron beams is launched into a resist film a scatteringphenomenon takes place to degrade a pattern profile.

Another problem of electron beams is in that, even when electron beamsare irradiated in a reduced beam diameter with the intention of formingfine patterns, the area irradiated with them is broadened due to thescattering phenomenon described above and thereby the resolution islowered.

These problems of irradiation with electron beams are, however, solvedwell by the present compositions.

DETAILED DESCRIPTION OF THE INVENTION

The invention includes:

1. A positive photosensitive composition comprising:

(A) a compound capable of generating a sulfonic acid represented byformula (X) above upon irradiation with one of an actinic ray andradiation; and

(B) a resin capable of decomposing under the action of an acid toincrease the solubility in an alkali developer (hereinafter referred toas “the first composition”), and

2. A positive photosensitive composition comprising:

(A) a compound capable of generating a sulfonic acid represented byformula (X) below upon irradiation with one of an actinic ray andradiation;

(C) a dissolution-inhibiting compound having a molecular weight of notmore than 3,000 which contains an acid-decomposable group and canincrease the solubility in an alkali developer by the action of an acid;and

(D) a resin insoluble in water and soluble in an alkali developer(hereinafter referred to as “the second composition”).

When the simple expression of “positive photosensitive composition” or“composition” is used hereinafter, it includes both the firstcomposition and the second composition mentioned above.

Additionally, the term “an actinic ray and radiation” used in theinvention is intended to include far ultraviolet rays (such as KrFexcimer laser and ArF excimer laser), electron beams, X-rays and ionbeams.

The compounds, resins and other components contained in the presentpositive photosensitive compositions are described below in greaterdetail.

[Description of Components Contained in Compositions]

<<Photo-Acid Generators>>

Photo-acid generators used in the invention are compounds capable ofgenerating sulfonic acids represented by the foregoing formula (X) uponirradiation with actinic rays or radiation (hereinafter referred to as“Component (A)” or “sulfonic acid-generators”). Of these compounds, thecompounds capable of generating sulfonic acids represented by theforegoing formula (X′) are preferred over the others.

In formula (X) or (X′), the alkyl groups represented by R_(1a) toR_(13a) groups include alkyl groups having 1 to 12 carbon atoms, such asmethyl, ethyl, propyl, n-butyl, sec-butyl and t-butyl, which may havesubstituent groups.

The haloalkyl groups represented by R_(1a) to R_(13a) groups are alkylgroups substituted with a halogen atom, and include alkyl groups having1 to 12 carbon atoms which are substituted with at least one of fluorineatom, chlorine atom, bromine atom and iodine atom, and the preferablehaloalkyl groups are alkyl groups substituted with a fluorine atom.

The halogen atoms represented by R_(1a) to R_(13a) groups includefluorine, chlorine and iodine atoms.

As examples of substitutents the foregoing alkyl groups may have,mention may be made of alkoxy groups having 1 to 4 carbon atoms,halogenatoms (e.g., fluorine, chlorine, iodine), aryl groups having 6 to10 carbon atoms, alkenyl groups having 2 to 6 carbon atoms, a cyanogroup, a hydroxyl group, a carboxyl group, alkoxycarbonyl groups and anitro group.

Examples of a hetero atom-containing divalent linkage group representedby A₁, A₂ or A include —O—, —S—, —CO—, —COO—, —CONR—, —SO₂NR—, —CONRCO—,—SO₂NRCO—, —SO₂NRSO₂— and —OCONR—.

Herein, R represents a hydrogen atom, or an alkyl group having 1 to 10carbon atoms, which may be substituted with a halogen atom, a hydroxylgroup or an alkoxy group. Further, R may combine with at least one ofthe R_(1a) to R_(13a) groups to form a ring. And the ring formed maycontain a linkage group, such as an oxygen atom, a nitrogen atom, asulfur atom or —CO—.

As the sulfonic acids of formula (X) or (X′), cases are suitable whereat least one of the R_(1a) to R_(13a) groups represents a halogen atom,especially a fluorine atom. In particular, it is preferable that eitherthe R_(12a) or R_(13a) group or both of these groups in formula (X) or(X′) are fluorine atoms.

Of these sulfonic acids, CF₃(CF₂)_(k)[A(CF₂)_(k′)]_(q)SO₃H,CF₃(CF₂)_(k)(CH₂)_(k′)SO₃H, CH₃(CH₂)_(k)(CF₂)_(k′)SO₃H (wherein k is aninteger of 0 to 12, k′ is an integer of 1 to 12, and A and qrespectively have the same meanings as the above) and compoundsrepresented by the following formula are preferred over the others,especially CF₃CF₂—O—CF₂CF₂SO₃H is preferable:

Herein, m₁ is an integer of 0 to 3, preferably 0 or 1, and A₁ preferablyrepresents a single bond, —O—, —CONR— or —COO—.

Further, it is preferable that the number of fluorine atoms contained inthe sulfonic acid of formula (X) be not more than 20, preferably notmore than 15, particularly preferably not more than 9. Furthermore, inview of improvement in affinity of the acid generator for water, it ispreferable that the number of fluorine atoms contained in the sulfonicacid is smaller than that of hydrogen atoms.

As Component (A) of the present invention, sulfonium or iodonium saltsof sulfonic acids represented by the foregoing formula (X) are suitablefrom the viewpoints of sensitivity and resolution.

The sulfonium salts are more suitable, and they enable furtherimprovement in storage stability.

Specifically, compounds having structures represented by the followingformulae (I) to (III) are preferred as Component (A):

wherein R₁ to R₃₇ groups each represent a hydrogen atom, astraight-chain, branched or cyclic alkyl group, a straight-chain,branched or cyclic alkoxy group, a hydroxyl group, a halogen atom or an—S—R₃₈ group, R₃₈ represents a straight-chain, branched or cyclic alkylgroup or an aryl group, and X⁻ represents an anion of sulfonic acidrepresented by formula (X).

As examples of a straight-chain or branched alkyl group represented byR₁ to R₃₈ groups each, mention may be made of alkyl groups having 1 to 4carbon atoms, including methyl, ethyl, propyl, n-butyl, sec-butyl andt-butyl groups, which each may have a substituent group.

As examples of a cyclic alkyl group represented by R₁ to R₃₈ groupseach, mention may be made of cycloalkyl groups having 3 to 8 carbonatoms, including cyclopropyl, cyclopentyl and cyclohexyl groups, whicheach may have a substituent group.

As examples of an alkoxy group represented by R₁ to R₃₇ groups each,mention may be made of alkoxy groups having 1 to 4 carbon atoms,including methoxy, ethoxy, hydroxyethoxy, propoxy, n-butoxy, isobutoxy,sec-butoxy and t-butoxy groups.

As examples of a halogen atom represented by R₁ to R₃₇ groups each,mention may be made of fluorine, chlorine, bromine and iodine atoms.

As examples of an aryl group represented by R₃₈, mention may be made ofunsubstituted or substituted aryl groups having 6 to 14 carbon atoms,including phenyl, tolyl, methoxyphenyl and naphthyl groups.

As examples of a substituent group which each of the groups as recitedabove may have, mention may be made of alkoxy groups having 1 to 4carbon atoms, halogen atoms (e.g., fluorine, chlorine, iodine), arylgroups having 6 to 10 carbon atoms, alkenyl groups having 2 to 6 carbonatoms, a cyano group, a hydroxyl group, a carboxyl group, alkoxycarbonylgroups and a nitro group.

Every iodonium compound of formula (I) and sulfonium compound of formula(II) or (III) which can be used in the invention contains as counteranion X⁻ an anion of sulfonic acid represented by formula (X).

Such an anion is an anion (—SO₃ ⁻) formed by departure of a hydrogenatom from the sulfonic acid group (—SO₃H).

In addition, aromatic ring-free sulfonium salts and phenacyl sulfoniumsalts are also suitable as Component (A)

As examples of such aromatic ring-free sulfonium salts, mention may bemade of salts containing sulfonium represented by the following formula(IV) as their cation:

wherein R^(1b) to R^(3b) groups independently represent an organic grouphaving no aromatic ring. The term “aromatic ring” used herein isintended to include hetero atom-containing aromatic rings also.

The number of carbon atoms contained in the aromatic ring-free organicgroup as each of the R^(1b) to R^(3b) groups is generally from 1 to 30,preferably from 1 to 20.

Specifically, it is preferable that R^(1b) to R^(3b) groups eachrepresent an alkyl group, a 2-oxoalkyl group, an alkoxycarbonylmethylgroup, an allyl group or a vinyl group, preferably a straight-chain,branched or cyclic 2-oxoalkyl group, or an alkoxycarbonylmethy group,particularly preferably a straight-chain or branched 2-oxoalkyl group.

The alkyl group as each of R^(1b) to R^(3b) groups, though may have anyof straight-chain, branched and cyclic forms, preferably includesstraight-chain or branched alkyl groups having 1 to 10 carbon atoms(such as methyl, ethyl, propyl, butyl, pentyl) and cycloalkyl groupshaving 3 to 10 carbon atoms (e.g., cyclopentyl, cyclohexyl, norbornyl).

The 2-oxoalkyl group as each of R^(1b) to R^(3b) groups, though may haveany of straight-chain, branched and cyclic forms, preferably includesthe groups having the same alkyl moieties as the alkyl groups recitedabove and >C═O at the 2-positions thereof.

The alkoxy moiety of an alkoxycarbonylmethyl group as each of R^(1b) toR^(3b) groups is preferably an alkyl group having 1 to 5 carbon atoms(e.g., methyl, ethyl, propyl, butyl, pentyl).

Each of the groups represented by R^(1b) to R^(3b) may further besubstituted with a halogen atom, an alkoxy group (containing, e.g., 1 to5 carbon atoms), a hydroxyl group, a cyano group or a nitro group.

Any two of R^(1b) to R^(3b) groups may combine with each other to from aring structure, and in the ring formed may be contained an oxygen atom,a sulfur atom, an ester linkage, an amide linkage or a carbonyl group.As examples of a group formed by combining any two of R^(1b) to R^(3b)groups, mention may be made of alkylene groups (e.g., butylene,pentylene).

From the viewpoint of photo-reactivity, it is preferable that one ofR^(1b) to R^(3b) groups is a group having a carbon-carbon double bond ora carbon-oxygen double bond.

As to the compounds represented by formula (IV), a structure may betaken that at least one of R^(1b) to R^(3b) groups present in onecompound is bound to at least one of R^(1b) to R^(3b) groups present inanother compound.

The aromatic ring-free sulfonium salts contain anions of sulfonic acidsrepresented by formula (X) as their counter anions.

Examples of a compound having a phenacyl sulfonium salt structureinclude compounds represented by the following formula (V):

wherein R_(1c) to R_(5c) groups independently represent a hydrogen atom,an alkyl group, an alkoxy group, or a halogen atom; R_(6c) and R_(7c)groups independently represent a hydrogen atom, an alkyl group, or anaryl group; Rx and Ry groups independently represent an alkyl group, a2-oxoalkyl group, an alkoxycarbonylmethyl group, an allyl group or avinyl group; or at least two of R_(1c) to R_(7c) groups may combine witheach other to form a ring structure, or Rx and Ry may combine with eachother to form a ring structure, and the ring structure formed maycontain an oxygen atom, a sulfur atom, an ester linkage or an amidelinkage; and X⁻ is an anion of sulfonic acid represented by formula (X).

The alkyl groups as R_(1c) to R_(5c) may have any of straight-chain,branched and cyclic forms, and examples thereof include alkyl groupshaving 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms,straight-chain and branched alkyl groups (such as a methyl group, anethyl group, straight-chain and branched propyl groups, straight-chainand branched butyl groups, and straight-chain and branched pentylgroups), and cycloalkyl groups having 3 to 8 carbon atoms (such ascyclopentyl and cyclohexyl groups).

The alkoxy groups as R_(1c) to R_(5c) may have any of straight-chain,branched and cyclic forms, and examples thereof include alkoxy groupshaving 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms,straight-chain and branched alkoxy groups (such as a methoxy group, anethoxy group, straight-chain and branched propoxy groups, straight-chainand branched butoxy groups, and straight-chain and branched pentoxygroups), and cycloalkoxy groups having 3 to 8 carbon atoms (such ascyclopentyloxy and cyclohexyloxy groups).

As to the compounds represented by formula (V), it is preferable thatanyone of R_(1c) to R_(5c) be a straight-chain, branched or cyclic alkylor alkoxy group. Further, the total number of carbon atoms contained inR_(1c) to R_(5c) groups is preferably from 2 to 15. By being sodesigned, the compounds can have increased solvent solubilities andinhibit particle generation upon storage.

Examples of alkyl groups as R_(6c) and R_(7c) include the same alkylgroups as R_(1c) to R_(5c). And examples of aryl groups as R_(6c) andR_(7c) include aryl groups having 6 to 14 carbon atoms (e.g., phenyl).

Examples of alkyl groups as Rx and Ry include the same alkyl groups asR_(1c) to R_(5c).

The 2-oxoalkyl group as Rx and Ry groups each includes the groupshaving >C═O at the 2-positions of the alkyl groups recited as those forR_(1c) to R_(5c) groups.

Examples of an alkoxy moiety in the alkoxycarbonylmethyl group as Rx andRy groups each include the same alkoxy groups as recited above withrespect to the R_(1c) to R_(5c) groups.

Examples of a group formed by combining Rx with Ry include a butylenegroup and a pentylene group.

Examples of a compound usable as Component (A) (including compoundsrepresented by formulae (I) to (V)) are illustrated below. However,these examples should not be construed as limiting the scope of theinvention in any way.

The Compounds (A-14), (A-15), (A-19), (A-20), (A-50), (A-51) and (A-52)illustrated above are each prepared using as starting materials sulfonicacids synthesized via telomerization. Therefore, each of them is amixture containing at least 60% of the compound illustrated and sulfonicacid salts differing in fluoroalkyl chain length.

Compounds represented by formula (I) as Component (A) can be synthesizedby reacting aromatic compounds with periodate, and then subjecting theresulting iodonium salts to salt exchange reaction using thecorresponding sulfonic acids.

Compounds represented by formula (II) and those represented by formula(III) can be synthesized by reacting aryl Grignard reagents, such asarylmagnesium bromides, with substituted or unsubstituted phenylsulfoxide, and then subjecting the resulting triarylsulfonium halides tosalt exchange reaction using the corresponding sulfonic acids.

Further, those compounds can be synthesized using a method in whichsubstituted or unsubstituted phenyl sulfoxide and the correspondingaromatic compounds are condensed in the presence of an acid catalyst,such as methanesulfonic acid/diphosphorus pentoxide or aluminumchloride, and then the condensation products are subjected to saltexchange reaction, or a method of condensing diaryl iodonium salts anddiaryl sulfide in the presence of a catalyst such as copper acetate, andthen subjecting the condensation products to salt exchange reaction.

The salt exchange reaction can be effected by a method in which thehalide salts once derived are converted to sulfonic acid salts with theaid of a silver reagent, such as silver oxide, or ion exchange resins.The sulfonic acids or sulfonic acid salts used for the salt exchangereaction are commercially available or can be prepared by hydrolysis ofcommercially available sulfonic acid halides.

The foregoing compounds as Component (A) can be used alone or as variouscombinations thereof.

The suitable proportion of the compound(s) as Component (A) in thepresent positive photosensitive composition is from 0.1 to 20 weight %,preferably from 0.5 to 10 weight %, particularly preferably from 1 to 7weight %, on a solids basis.

<Other Photo-Acid Generators Usable Together with Compounds as Component(A)>

In addition to the compounds defined above as Component (A), othercompounds capable of decomposing upon irradiation with actinic rays orradiation to generate acids may be used in the invention.

The mole ratio of the compound(s) as Component (A) to photo-acidgenerators used together therewith is generally from 100/0 to 20/80,preferably from 100/0 to 40/60, particularly preferably from 100/0 to50/50.

The photo-acid generators used together with the compound(s) asComponent (A) can be selected preferably from photo-initiators forcationic photopolymerization, photo-initiators for radicalphotopolymerization, photodecolouring agents for dyes, photodiscolouringagents, compounds known to be used in microresist and capable ofgenerating acids by irradiation with actinic rays or radiation, ormixtures of two or more of the agents recited above.

Examples of such photo-acid generators include onium salts, such asdiazonium salts, ammonium salts, phosphonium salts, iodonium salts,sulfonium salts, selenonium salts and arsonium salts, organic halogencompounds, organometal-organic halide compounds, photo-acid generatorshaving o-nitrobenzyl type protective groups, compounds capable ofgenerating sulfonic acid by photolysis, typified by iminosulfonates, anddisulfone compounds.

In addition, polymers having main or side chains into which areintroduced those groups or compounds capable of generating acids uponirradiation with actinic rays or radiation, as described in U.S. Pat.No. 3,849,137, German Patent 3914407, JP-A-63-26653, JP-A-55-164824,JP-A-62-69263, JP-A-63-146038, JP-A-63-163452, JP-A-62-153853 andJP-A-63-146029, can be used.

Also, the compounds capable of generating acids under light, asdescribed in U.S. Pat. No. 3,779,778 and European Patent 126,712, can beused.

Of the above-recited photo-acid generators which can be used togetherwith the compound(s) as Component (A), the following compounds are usedto particular advantage.

(1) Trihalomethyl-substituted oxazole compounds represented by thefollowing formula (PAG1) or trihalomethyl-substituted s-triazinecompounds represented by the following formula (PAG2):

In the above formulae, R²⁰¹ represents a substituted or unsubstitutedaryl or alkenyl group, R²⁰² represents a substituted or unsubstitutedaryl, alkenyl or alkyl group, or —C(Y)₃, and Y represents a chlorine orbromine atom.

Examples of such compounds are illustrated below, but the compoundsusable in the invention should not be construed as being limited tothese examples.

(2) Iodonium salts represented by the following formula (PAG3) orsulfonium salts represented by the following formula (PAG4):

In the above formulae, Ar¹ and Ar² independently represent a substitutedor unsubstituted aryl group. Examples of a substituent suitable for thearyl group include an alkyl group, a haloalkyl group, a cycloalkylgroup, an aryl group, an alkoxy group, a nitro group, a carboxyl group,an alkoxycarbonyl group, a hydroxyl group, a mercapto group and ahalogen atom.

R²⁰³, R²⁰⁴ and R²⁰⁵ independently represent a substituted orunsubstituted alkyl or aryl group, preferably a 6-14C aryl group whichmay have a substituent, or a 1-8C alkyl group which may have asubstituent.

Examples of a substituent suitable for such an aryl group include a 1-8Calkoxy group, a 1-8C alkyl group, a nitro group, a carboxyl group, ahydroxyl group and a halogen atom, and those for such an alkyl groupinclude a 1-8C alkoxy group, a carboxyl group and an alkoxycarbonylgroup.

Z⁻ represents a counter anion, with examples including BF₄ ⁻, AsF₆ ⁻,PF₆ ⁻, SbF₆ ⁻, SiF₆ ⁻, ClO₄ ⁻, perfluoroalkanesulfonic acid anions suchas CF₃SO₃ ⁻, pentafluorobenzenesulfonic acid anion, condensedpolynuclear aromatic sulfonic acid anions such as naphthalene-1-sulfonicacid anion, anthraquinonesulfonic acid anion, and sulfonic acidgroup-containing dyes. However, Z⁻ should not be construed as beinglimited to these examples.

Further, any two among R²⁰³, R²⁰⁴ and R²⁰⁵, or Ar¹ and Ar² may be boundto each other via a single bond or a substituent.

Examples of onium salts as defined above are illustrated below. However,the onium salts usable in the invention should not be construed as beinglimited to these examples.

The onium salts represented by the foregoing formulae (PAG3) and (PAG4)are known compounds and can be synthesized using the methods asdescribed in, e.g., U.S. Pat. Nos. 2,807,648 and 4,247,473, orJP-A-53-101331.

(3) Disulfone compounds represented by the following formula (PAG5) oriminosulfonate compounds represented by the following formula (PAG6):

In the above formulae, Ar³ and Ar⁴ independently represent a substitutedor unsubstituted aryl group, R²⁰⁶ represents a substituted orunsubstituted alkyl or aryl group, and A represents a substituted orunsubstituted alkylene, alkenylene or arylene group.

Examples of those compounds are illustrated below, but these examplesshould not be construed as limiting the scope of the disulfone oriminosulfonate compounds usable in the invention.

(4) Diazodisulfone compounds represented by the following formula(PAG7):

In the above formula, R represents a straight-chain, branched or cyclicalkyl group, or an unsubstituted or substituted aryl group.

Examples of such compounds are illustrated below, but these compoundsshould not be construed as limiting the scope of the diazodisulfonecompounds usable in the invention.

Of the compounds illustrated above as photo-acid generators usabletogether with the compound(s) as Component (A), the following compoundsare preferred in particular:

Next the present compounds of formulae (I) to (III) are illustratedbelow in more detail.

[1-1] Present Iodonium Salt Compounds Represented by Formula (I)

Each of R₂₈ to R₃₇ groups in the foregoing formula (I) represents ahydrogen atom, a straight-chain or branched alkyl group having 1 to 4carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, a alkoxygroup having 1 to 4 carbon atoms, a hydroxyl group, a halogen atom, oran —S—R₃₈ group.

Herein, R₃₈ represents a straight-chain or branched alkyl group having 1to 12 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, or anaryl group having 6 to 14 carbon atoms.

Examples of a straight-chain or branched alkyl group having 1 to 4carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkoxygroup having 1 to 4 carbon atoms as R₂₈ to R₃₇ each and examples of anaryl group as R₃₈ include the same ones as recited hereinbefore asexamples of the corresponding groups respectively.

X⁻ is an anion of sulfonic acid represented by the foregoing formula(X), preferably an anion of sulfonic acid represented by the foregoingformula (X′).

In formula (X) or (X′), the alkyl groups as R_(1a) to R_(13a) groupsinclude alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl,propyl, n-butyl, sec-butyl and t-butyl, which may have substituentgroups.

The haloalkyl groups represented by R_(1a) to R_(13a) groups are alkylgroups substituted with a halogen atom, and include alkyl groups having1 to 12 carbon atoms which are substituted with at least one of fluorineatom, chlorine atom, bromine atom and iodine atom, and the preferablehaloalkyl groups are alkyl groups substituted with a fluorine atom.

The halogen atoms as R_(1a) to R_(13a) groups include fluorine, chlorineand iodine atoms.

As examples of substitutents the foregoing alkyl groups may have,mention may be made of alkoxy groups having 1 to 4 carbon atoms,halogenatoms (e.g., fluorine, chlorine, iodine), aryl groups having 6 to10 carbon atoms, alkenyl groups having 2 to 6 carbon atoms, a cyanogroup, a hydroxyl group, a carboxyl group, alkoxycarbonyl groups and anitro group.

Examples of a hetero atom-containing divalent linkage group as A₁, A₂ orA include —O—, —S—, —CO—, —COO—, —CONR—, —SO₂NR—, —CONRCO—, —SO₂NRCO—,—SO₂NRSO₂— and —OCONR—.

Herein, R represents a hydrogen atom, or a 1-10C alkyl group which maybe substituted with a halogen atom, a hydroxyl group or an alkoxy group.Further, R may combine with at least one of the R_(1a) to R_(13a) groupsto form a ring. And the ring formed may contain a linkage group, such asan oxygen atom, a nitrogen atom, a sulfur atom or —CO—.

As the sulfonic acids of formula (X) or (X′), cases are suitable whereat least one of the R_(1a) to R_(13a) groups represents a halogen atom,especially a fluorine atom. In particular, it is preferable that eitherthe R₁₂, or R_(13a) group or both of these groups in formula (X) or (X′)are fluorine atoms.

Of these sulfonic acids, CF₃(CF₂)_(k)[A(CF₂)_(k′)]_(q)SO₃H,CF₃(CF₂)_(k)(CH₂)_(k′)SO₃H, CH₃(CH₂)_(k)(CF₂)_(k′)SO₃H (wherein k is aninteger of 0 to 12, k′ is an integer of 1 to 12, and A and qrespectively have the same meanings as the above) and compoundsrepresented by the following formula are preferred over the others,especially CF₃CF₂—O—CF₂CF₂SO₃H is preferred:

Herein, m₁ is an integer of 0 to 3, preferably 0 or 1, and A₁ preferablyrepresents a single bond, —O—, —CONR— or —COO—.

Further, it is preferable that the number of fluorine atoms contained inthe sulfonic acid of formula (X) be not more than 20, preferably notmore than 15, particularly preferably not more than 9. Furthermore, inview of improvement in affinity of the acid generator for water, it ispreferable that the number of fluorine atoms contained in the sulfonicacid is smaller than that of hydrogen atoms.

[1-2] Present Sulfonium Salt Compounds Represented by Formula (II)

Each of R₁ to R₁₅ groups in the foregoing formula (II) represents ahydrogen atom, a straight-chain or branched alkyl group having 1 to 4carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkoxygroup having 1 to 4 carbon atoms, a hydroxyl group, a halogen atom, oran —S—R₃₈ group.

Herein, R₃₈ represents a straight-chain or branched alkyl group having 1to 12 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, or anaryl group having 6 to 14 carbon atoms.

Examples of a straight-chain or branched alkyl group having 1 to 4carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkoxygroup having 1 to 4 carbon atoms as R₁ to R₁₅ each and examples of anaryl group as R₃₈ include the same ones as recited hereinbefore asexamples of the corresponding groups respectively.

X⁻ is an anion of sulfonic acid represented by the foregoing formula(X).

The anion of sulfonic acid represented by formula (X) conforms to thecontents (including specific examples and suitable examples) explainedabout the iodonium salt compounds [1-1] of the foregoing formula (I).

[1-3] Present Sulfonium Salt Compounds Represented by Formula (III)

Each of R₁₆ to R₂₇ groups in the foregoing formula (III) represents ahydrogen atom, a straight-chain or branched alkyl group having 1 to 4carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkoxygroup having 1 to 4 carbon atoms, a hydroxyl group, a halogen atom, oran —S—R₃₈ group.

Herein, R₃₈ represents a straight-chain or branched alkyl group having 1to 12 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, or anaryl group having 6 to 14 carbon atoms.

Examples of a straight-chain or branched alkyl group having 1 to 4carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkoxygroup having 1 to 4 carbon atoms as R₁₆ to R₂₇ each and examples of anaryl group as R₃₈ include the same ones as recited hereinbefore asexamples of the corresponding groups respectively.

X⁻ is an anion of sulfonic acid represented by the foregoing formula(X).

The anion of sulfonic acid represented by formula (X) conforms to thecontents (including specific examples and suitable examples) explainedabout the iodonium salt compounds [1-1] of the foregoing formula (I).

<<(B) Resin Capable of Increasing Solubility in Alkali Developer UnderAction of Acid>>

In the invention, the resin (B) is an essential component of the firstcomposition.

The resin (B) has groups that can be decomposed by the action of an acid(hereinafter referred to as “acid-decomposable groups” too). Theacid-decomposable groups are contained in at least either main chain orside chains of the resin, preferably in side chains of the resin.

As examples of an acid-decomposable group, mention may be made of groupscapable of forming at least one of a carboxylic acid and a phenolichydroxy group by being decomposed by the action of an acid.

The resin (B) used in the invention is selected preferably depending onthe kind of light for exposure or rays for irradiation. Specifically, itis preferable that the kind of resin (B) be selected in view oftransparency and sensitivity to exposure light or irradiation beams, andfurther with consideration of dry etching resistance.

Examples of a resin (B) used suitably in a photosensitive composition toundergo exposure to KrF excimer laser or irradiation with electron beamsor X-ray include resins containing acid-decomposable groups and aromaticrings (resins of polyhydroxystyrene type).

Examples of a resin (B) used preferably in a photosensitive compositionto undergo exposure to ArF excimer laser include resins containing noaromatic rings but containing acid-decomposable groups andcycloaliphatic structures.

Now, resins included in the resin (B) used suitably in a photosensitivecomposition to undergo exposure to KrF excimer laser or irradiation withelectron beams or X-ray are illustrated below in detail.

Groups preferred as an acid-decomposable group are a group representedby —COOA⁰ and a group represented by —O—B⁰. Groups containing thesegroups are represented by —R⁰—COOA⁰ and —Ar—O—B⁰ respectively.

Therein, A⁰ represents —C(R⁰¹)(R⁰²)(R⁰³) —Si(R⁰¹)(R⁰²)(R⁰³) or—C(R⁰⁴)(R⁰⁵)—O—R⁰⁶. B⁰ represents A⁰ or —CO—O-A⁰. R⁰, R⁰¹ to R⁰⁶, and Arhave the same meanings as those described hereinafter respectively.

Suitable examples of an acid-decomposable group include a silyl ethergroup, a cumyl ester group, an acetal group, a tetrahydropyranyl ethergroup, an enol ether group, an enol ester group, a tertiary alkyl ethergroup, a tertiary alkyl ester group and a tertiary alkylcarbonate group.Of these groups, a tertiary alkyl ester group, a tertiary alkylcarbonategroup, a cumyl ester group, an acetal group and a tetrahydropyranylether group are preferred over the others. In particular, an acetalgroup is well suited for use as the acid-decomposable group.

The acid-decomposable resin contains preferably a repeating unit havingthe acid-decomposable group in an amount of 5 to 70 mole %, morepreferably 10 to 60 mole %, far more preferably 15 to 50 mole %, basedon the total repeating units.

Examples of a parent resin to which the acid-decomposable groups asrecited above are bonded as side chains include alkali-soluble resinscontaining —OH or —COOH groups, preferably —R⁰—COOH or —Ar—OH groups, intheir side chains. As examples of such resins, mention may be made ofalkali-soluble resins illustrated below.

The suitable alkali dissolution rate of such an alkali-soluble resin isnot slower than 170 angstrom/sec, preferably not slower than 330angstrom/sec, as measured in 0.261 N tetramethylammonium hydroxide(TMAH) at 23° C.

From the viewpoint of attaining a rectangular profile, alkali-solubleresins having high transparency to far ultraviolet rays or excimer laserbeams are used to advantage. Specifically, preferable alkali-solubleresins are those having their transmittances at 248 nm in the range of20 to 90% when they are formed into 1 μm-thick films.

Examples of alkali-soluble resins preferred in particular from thoseviewpoints include poly(o-, m- or p-hydroxystyrene), copolymer of o-, m-and p-hydroxystyrenes, hydrogenated poly(hydroxystyrene), halogen oralkyl-substituted poly(hydroxystyrene), partially O-alkylated orO-acylated poly(hydroxystyrene), styrene/hydroxystyrene copolymer,α-methylstyrene/hydroxystyrene copolymer, and hydrogenated novolakresin.

Resins usable in the invention, which contain acid-decomposable groups,can be prepared by reacting alkali-soluble resins with precursors ofacid-decomposable groups, or by copolymerizing alkali-solubleresin-forming monomers to which acid-decomposable groups are bonded andother monomers, as disclosed in European Patent 254853, JP-A-2-25850,JP-A-3-223860 and JP-A-4-251259.

Resins suitable as acid-decomposable resins in the invention arepoly(hydroxystyrene)s whose phenolic hydroxyl groups are partially ortotally protected by acid-decomposable groups. The acid-decomposablegroups preferred herein are acetal groups. By protection with acetalgroups, variations in performance with the lapse of time fromirradiation till post-baking can be reduced. As the acetal groups,1-alkoxyethyl acetal groups are suitable. And more suitable acetalgroups are cycloaliphatic or aryl group-containing 1-alkoxyethyl acetalgroups. By using these acetal groups, dry etching resistance isenhanced.

Examples of a resin containing acid-decomposable groups which can beused in the invention are recited below, but these examples should notbe construed as limiting the scope of the invention.

-   p-t-Butoxystyrene/p-hydroxystyrene copolymer-   p-(t-Butoxycarbonyloxy)styrene/p-hydroxystyrene copolymer-   p-(t-Butoxycarbonylmethyloxy)styrene/p-hydroxystyrene copolymer-   4-(t-Butoxycarbonylmethyloxy)-3-methylstyrene/4-hydroxy-3-methylstyrene    copolymer-   p-(t-Butoxycarbonylmethyloxy) styrene/p-hydroxystyrene (10%    hydrogenated) copolymer-   m-(t-Butoxycarbonylmethyloxy)styrene/m-hydroxystyrene copolymer-   o-(t-Butoxycarbonylmethyloxy)styrene/o-hydroxystyrene copolymer-   p-(Cumyloxycarbonylmethyloxy)styrene/p-hydroxystyrene copolymer-   Cumyl methacrylate/methyl methacrylate copolymer-   4-t-Butoxycarbonylstyrene/dimethyl maleate copolymer-   Benzyl methacrylate/tetrahydropyranyl methacrylate copolymer-   p-(t-Butoxycarbonylmethyloxy)styrene/p-hydroxystyrene/styrene    copolymer-   p-t-Butoxystyrene/p-hydroxystyrene/fumaronitrile copolymer-   t-Butoxystyrene/hydroxyethyl methacrylate copolymer-   Styrene/N-(4-hydroxyphenyl)maleimide/N-(4-t-butoxycarbonyl    oxyphenyl)maleimide copolymer-   p-Hydroxystyrene/t-butyl methacrylate copolymer-   Styrene/p-hydroxystyrene/t-butyl methacrylate copolymer-   p-Hydroxystyrene/t-butyl acrylate copolymer-   Styrene/p-hydroxystyrene/t-butyl acrylate copolymer-   p-(t-Butoxycarbonylmethyloxy) styrene/p-hydroxystyrene/N-me    thylmaleimide copolymer-   t-Butyl methacrylate/1-adamantylmethyl methacrylate copolymer-   p-Hydroxystyrene/t-butyl acrylate/p-acetoxystyrene copolymer-   p-Hydroxystyrene/t-butyl acrylate/p-(t-butoxycarbonyloxy)styrene    copolymer-   p-Hydroxystyrene/t-butyl    acrylate/p-(t-butoxycarbonylmethyloxy)styrene copolymer

In the invention, resins containing repeating structural unitsrepresented by the following formulae (IV) and (V) are preferred asresins having acid-decomposable groups (Component (B)). Thephotosensitive compositions using these resins can have high resolutionand smaller variations in their performances during the period fromirradiation till baking.

In the above formula (IV), L represents a hydrogen atom, anunsubstituted or substituted straight-chain, branched or cyclic alkylgroup, or an unsubstituted or substituted aralkyl group.

Z represents an unsubstituted or substituted straight-chain, branched orcyclic alkyl group, or an unsubstituted or substituted aralkyl group.Further, Z may combine with L to form a 5- or 6-membered ring.

Examples of an alkyl group represented by L and Z each in formula (IV)include straight-chain, branched and cyclic alkyl groups having 1 to 20carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl,isobutyl, t-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, octyl anddodecyl groups.

Examples of groups preferred as substitutents of those alkyl groupsinclude an alkyl group, an alkoxy group, a hydroxyl group, a halogenatom, a nitro group, an acyl group, an acylamino group, a sulfonylaminogroup, an alkylthio group, an arylthio group and an aralkylthio group.As examples of a substituted alkyl group, mention may be made of acyclohexylethyl group, an alkylcarbonyloxymethyl group, analkylcarbonyloxyethyl group, an arylcarbonyloxyethyl group, anaralkylcarbonyloxyethyl group, an alkyloxymethyl group, an aryloxymethylgroup, an aralkyloxymethyl group, an alkyloxyethyl group, anaryloxyethyl group, an aralkyloxyethyl group, an alkylthiomethyl group,an arylthiomethyl group, an aralkylthiomethyl group, an alkylthioethylgroup, an arylthioethyl group and an aralkylthioethyl group. The alkylmoieties contained therein have no particular restrictions, but they maybe any of straight-chain, cyclic and branched ones. For instance, thesubstituted alkyl group may be a cyclohexylcarbonyloxyethyl group, at-butylcyclohexyl-carbonyloxyethyl or ann-butylcyclohexylcarbonyoxyethyl group. The aryl moieties contained inthe above-recited ones have no particular restrictions, too. Forinstance, the substituted alkyl group may be a phenyloxyethyl group.Those aryl moieties may be further substituted, and cyclohexylphenyloxyethyl group can be cited as an example of such a case. The aralkylmoieties also have no particular restrictions. For example,benzylcarbonyloxyethyl group may be such a substituted alkyl group.

As examples of an aralkyl group represented by L and Z each, mention maybe made of those containing 7 to 15 carbon atoms, such as a substitutedor unsubstituted benzyl group and a substituted or unsubstitutedphenetyl groups. Examples of groups preferred as substituents of aralkylgroups include an alkoxy group, a hydroxyl group, a halogen atom, anitro group, an acyl group, an acylamino group, a sulfonylamino group,an alkylthio group, an arylthio group and an aralkylthio group. Forinstance, the substituted aralkyl group may be an alkoxybenzyl group, ahydroxybenzyl group or a phenylthiophenetyl group.

Further, it is preferable that Z is a substituted alkyl or aralkylgroup, because improvement in edge roughness can be perceived in such acase. Examples of a substituent suitable for the alkyl group include acyclic alkyl group, an aryloxy group, an alkylcarboxy group, anarylcarboxy group and an aralkylcarboxy group, and examples of asubstituent suitable for the aralkyl group include an alkyl group, acyclic alkyl group and a hydroxyl group.

As examples of a 5- or 6-membered ring formed by combining L and Z,mention may be made of a tetrahydropyran ring and a tetrahydrofuranring.

The suitable ratio of the repeating structural units represented byformula (IV) to the repeating structural units represented by formula(V) in the resin is from 1/99 to 60/40, preferably from 5/95 to 50/50,particularly preferably from 10/90 to 40/60.

In the resin comprising the repeating structural units represented byformulae (IV) and (V), repeating structural units derived from othermonomers may further be contained.

Examples of the other monomers include hydrogenated hydroxystyrene;halogen-, alkoxy- or alkyl-substituted hydroxystyrenes; styrene;halogen-, alkoxy-, acyloxy- or alkyl-substituted styrenes; maleicanhydride; acrylic acid derivatives; methacrylic acid derivatives; andN-substituted maleimides, but these examples should not be construed aslimiting the scope of the invention.

The suitable molar ratio of the total structural units of formulae (IV)and (V) to the structural units derived from other monomers, or[(IV)+(V)]/[other monomers] ratio, is from 100/0 to 50/50, preferablyfrom 100/0 to 60/40, particularly preferably 100/0 to 70/30.

Examples of a resin comprising the repeating structural unitsrepresented by formulae (IV) and (V) and other resins usable in theinvention are illustrated below.

In the above structural formulae, Me stands for a methyl group, Etstands for an ethyl group, nBu stands for a n-butyl group, iso-Bu standsfor an iso-butyl group, and tBu stands for a t-butyl group.

In the case of using acetal groups as the acid-decomposable groups,cross-link regions linked by polyfunctional acetal groups may beintroduced in the polymer main chain by adding a polyhydroxy compound atthe stage of synthesis for the purpose of controlling alkali-dissolutionspeed and enhancing heat resistance. The amount of polyhydroxy compoundadded is from 0.01 to 5 mole %, preferably from 0.05 to 4 mole %, basedon the content of hydroxyl groups in the resin. As examples of apolyhydroxy compound, mention may be made of compounds having 2 to 6phenolic or alcoholic hydroxyl groups per molecule, preferably compoundshaving 2 to 4 hydroxyl groups per molecule, particularly preferablycompounds having 2 or 3 hydroxyl groups per molecule. More specifically,the following polyhydroxy compounds can be recited, but the inventionshould not be construed as being limited to these compounds.

The suitable weight average molecular weight (Mw) of the resin (B)having acid-decomposable groups is from 2,000 to 300,000. When the resinhas a weight average molecular weight less than 2,000, the thicknessreduction caused in the unexposed areas of the resulting resist film bydevelopment becomes great; while when the weight average molecularweight of the resin is greater than 300,000 the resin itself becomesslow in alkali-dissolution speed and causes reduction in sensitivity.Herein, the term “weight average molecular weight” is defined as thevalue measured by gel permeation chromatography (GPC) and calculated interms of polystyrene.

Secondly, resins as Component (B) which can be used to advantage inphotosensitive compositions suitable for exposure to ArF excimer laserare illustrated in greater detail.

Suitable examples of acid-decomposable groups contained in such resinsinclude groups represented by the following formulae (x) and (y)respectively, acid-decomposable groups having lactone structures, andacid-decomposable groups having cycloaliphatic structures. By havingthese acid-decomposable groups, the resins can have excellent storagestability.

In the above formulae, Ra, Rb and Rc are independent of each other andeach represents a hydrogen atom, or an unsubstituted or substitutedalkyl, cycloalkyl or alkenyl group. In the formula (x), however, atleast one of the Ra, Rb and Rc groups represents a group other thanhydrogen. Rd represents an unsubstituted or substituted alkyl, cyclalkylor alkenyl group. On the other hand, any two of the Ra, Rb and Rc groupsin formula (x), or any two of the Ra, Rb and Rd groups may combine witheach other to form a ring structure containing 3 to 8 carbon atoms.Further, the ring structure formed may contain a hetero atom. Examplesof such a ring structure include cyclopropyl, cyclopentyl, cyclohexyl,cycloheptyl, 1-cyclohexenyl, 2-tetrahydrofuranyl and 2-tetrahydropyranylgroups.

Za and Zb are independently of each other, and each represents an oxygenatom or a sulfur atom.

Suitable examples of an alkyl group as Ra to Rd each includeunsubstituted or substituted alkyl groups having 1 to 8 carbon atoms,such as methyl, ethyl, propyl, n-butyl, sec-butyl, hexyl, 2-ethylhexyland octyl groups. Suitable examples of a cycloalkyl group as Ra to Rdeach include unsubstituted or substituted cycloalkyl groups having 3 to8 carbon atoms, such as cyclopropyl, cyclopentyl and cyclohexyl groups.Suitable examples of an alkenyl group as Ra to Rd each includeunsubstituted or substituted alkenyl groups having 2 to 6 carbon atoms,such as vinyl, propenyl, allyl, butenyl, pentenyl, hexenyl andcyclohexenyl groups.

As suitable examples of substituents which the groups as recited abovecan have, mention may be made of a hydroxyl group, a halogen atom (e.g.,fluorine, chlorine, bromine, iodine), a nitro group, a cyano group, anamido group, a sulfonamido group, an alkyl group (e.g., methyl, ethyl,propyl, n-butyl, sec-butyl, hexyl, 2-ethylhexyl, octyl), an alkoxy group(e.g., methoxy, ethoxy, hydroxyethoxy, propoxy, hydroxypropoxy, butoxy),an alkoxycarbonyl group (e.g., methoxycarbonyl, ethoxycarbonyl), an acylgroup (e.g., formyl, acetyl, benzoyl), an acyloxy group (e.g., acetoxy,butylyloxy), and a carboxyl group.

Examples of repeating structural units having acid-decomposable groupsas recited above are illustrated below, but these examples should not beconstrued as limiting the scope of the invention.

Of the above-illustrated ones, the units (c1), (c7) and (C11) arepreferred over the others because they are superior inacid-decomposability in particular.

In the invention, it is preferable that the acid-decomposable resinshave lactone structures.

Herein, it is preferable that the lactone structures are present in theside chains of each resin. Specifically, the following repeating units(a1) to (a20) having lactone structures in side chains thereof can berecited.

As mentioned above, both cycloaliphatic and lactone structures may beprovided with acid-decomposable groups, or may not necessarily beprovided therewith.

Of the structural units illustrated above, the units (a1), (a12) and(a15) are preferred over the others, because they generally showacid-decomposability.

As examples of a monocyclic cycloaliphatic structure which can becontained in acid-decomposable resins, mention may be made of groupshaving monocyclic cycloaliphatic skeletons containing at least 3 carbonatoms, preferably 3 to 8 carbon atoms, such as cyclopropane,cyclobutane, cyclopentane and cyclohexane skeletons. As examples of apolycyclic cycloaliphatic structure which can be contained inacid-decomposable resins, mention may be made of groups havingpolycyclic cycloaliphatic skeletons containing at least 5 carbon atoms,preferably 7 to 25 carbon atoms, such as bicyclo-, tricyclo- andtetracycloaliphatic skeletons. More specifically, structures as recitedhereinafter are included in those structures.

On the other hand, the acid-decomposable group which may contain acycloaliphatic group may be a group containing an acid-decomposablestructure as a linkage and capable of being decomposed by the action ofan acid to release a cycloaliphatic group, or a group wherein a grouprepresented by the foregoing formula (x) or (y) is combined with ancycloaliphatic group directly or via a linkage group.

When monocyclic or polycyclic cycloaliphatic groups are contained inside chains of a resin, it is preferable that they be linked to the mainchain of the resin via tertiary ester groups.

Suitable examples of a repeating unit having such a monocyclic orpolycyclic cycloaliphatic structure as mentioned above includestructural units represented by the following formulae (XII) to (XV):

The formulae (XII) to (XIV) are explained first, and an explanation ofthe formula (XV) follows them.

In formulae (XII) to (XIV), each of the substituent groups attached tothe main chain of each repeating unit, namely R¹¹, R¹² and R¹⁴ to R¹⁶,represents a hydrogen atom, a halogen atom, a cyano group, an alkylgroup or a haloalkyl group. These substituent groups may be the same asor different from each other.

Examples of an alkyl group represented by R¹¹, R¹² and R¹⁴ to R¹⁶ eachinclude hydrocarbon groups having 1 to 4 carbon atoms, such as methyl,ethyl, propyl, n-butyl and sec-butyl groups.

As examples of a haloalkyl group represented by R¹¹, R¹² and R¹⁴ to R¹⁶each, mention may be made of alkyl groups having 1 to 4 carbon atoms,whose hydrogen atoms are replaced partially or totally by halogen atoms.Herein, it is preferable for the halogen atoms to include fluorine,chlorine and bromine atoms. More specifically, the haloalkyl groupincludes fluoromethyl group, chloromethyl group, bromomethyl group,fluoroethyl group, chloroethyl group and bromoethyl group.

These alkyl and haloalkyl groups may further have substituents otherthan halogen atoms.

The substituent group R¹³ represents a cyano group, —CO—OR²³ or—CO—NR²⁴R²⁵.

Herein, R²³ represents a hydrogen atom, an alkyl group, a cycloalkylgroup, alkenyl group, or an acid-decomposable group. Examples of anacid-decomposable group include the same ones as recited above. Forinstance, the compounds having the same repeating structural units asdescribed above are preferred. The alkyl, cycloalkyl or alkenyl grouprepresented by R²³ may further have a substituent.

R²⁴ and R²⁵ each represent a hydrogen atom, an alkyl group, a cycloalkylgroup or an alkenyl group. Herein, the alkyl, cycloalkyl and alkenylgroups each may further have a substituent. R²⁴ and R²⁵ may be the sameor different. They may combine with each other to form a ring togetherwith the nitrogen atom. The ring structure preferably formed in thiscase includes 5- to 8-membered rings, such as pyrrolidine, piperidineand piperazine skeletons.

As the alkyl group represented by R²³ to R²⁵ each, alkyl groups having 1to 8 carbon atoms are suitable, with examples including methyl, ethyl,propyl, n-butyl, sec-butyl, hexyl, 2-ethylhexyl and octyl groups. As thecycloalkyl group, cycloalkyl groups having 3 to 8 carbon atoms aresuitable, with examples including cyclopropyl, cyclopentyl andcyclohexyl groups. As the alkenyl group, alkenyl groups having 2 to 6carbon atoms are suitable, with examples including vinyl, propenyl,allyl, butenyl, pentenyl, hexenyl and cyclohexenyl groups. These alkyl,cycloalkyl and alkenyl groups each may further have a substituent.

In formulae (XII) to (XIV), X₁, X₂ and X₃ in the substituent groupsformed into X₁-A₀, X₂-A₀ and X₃-A₀ respectively are each a single bondor a divalent group. Examples of such a divalent group include analkylene group, an alkenylene group, a cycloalkylene group, —O—, —SO₂—,—O—CO—R²⁶—, —CO—O—R²⁷—, and —CO—NR²⁸—R²⁹—. X₁, X₂ and X₃ may be the sameas or different from each other.

Of the groups represented by X₁ to X₃ each, the alkylene group, thealkenylene group and the cycloalkylene group include divalent groupshaving the same carbon skeletons as the alkyl group, the alkenyl groupand the cycloalkyl group that each of R¹¹, R¹² and R¹⁴ to R¹⁶ groups canrepresent, respectively.

R²⁶, R²⁷ and R²⁹ in —OCO—R²⁶—, —CO—O—R²⁷— and —CO—NR²⁸—R²⁹—, which X₁ toX₃ each can represent, are each a single bond or a divalent group.Examples of such a divalent group include an alkylene group, analkenylene group and a cycloalkylene group. Herein also, the alkylenegroup, the alkenylene group and the cycloalkylene group include divalentgroups having the same carbon skeletons as the alkyl group, the alkenylgroup and the cycloalkyl group that each of R¹¹, R¹² and R¹⁴ to R¹⁶groups can represent, respectively. By further combining with an ethergroup, an ester group, an amido group, an urethane group or an ureidogroup, each of those groups may form a divalent group in its entirety.R²⁶, R²⁷ and R²⁹ may be the same or different.

The substituent R²⁸ in —CO—NR²⁸—R²⁹— represented by each of X₁ to X₃groups represents, similarly to each of R²³ to R²⁵, a hydrogen atom, analkyl group, a cycloalkyl group or an alkenyl group. These alkyl,cycloalkyl and alkenyl groups may have substituent groups. R²⁸ may bethe same as either R²⁴ or R²⁵, or different from them.

Examples of alkyl, cycloalkyl and alkenyl groups R²⁸ can representinclude the same examples as included in the alkyl, cycloalkyl andalkenyl groups respectively each of R²³ to R²⁵ groups can represent.

The substituent A₀ bound to the main chain of repeating units via X₁, X₂or X₃ represents a monocyclic or polycyclic cycloaliphatic group.

As examples of a monocyclic cycloaliphatic group represented by A₀,mention may be made of groups having alicyclic skeletons containing atleast 3, preferably 3 to 8, carbon atoms, e.g., cycloaliphatic skeletonsincluding cyclopropane, cyclobutane, cyclopentane and cyclohexaneskeletons.

As examples of a polycyclic cycloalipahtic group represented by A₀,mention may be made of groups having alicyclic skeletons containing atleast 5, preferably 7 to 25, carbon atoms, such as bicyclo-, tricyclo-and tetracycloaliphatic skeletons. These monocyclic or polycycliccycloaliphatic skeleton-containing groups may further be substituted andbe increased in number of carbon atoms contained therein.

As examples of a substituent the polycyclic cycloaliphatic group mayhave, mention may be made of a hydroxyl group, a halogen atom, a nitrogroup, a cyano group, an amido group, a sulfonamido group and the alkylgroups recited in the description of R²³.

Therein, the halogen atom is a fluorine, chlorine, bromine or iodineatom. Examples of such a substituent further include an alkoxy group, analkoxycarbonyl group, an acyl group, an acyloxy group and a carboxylgroup.

As the alkoxy group, 1-8C alkoxy groups, such as methoxy, ethoxy,hydroxyethoxy, propoxy, hydroxypropoxy and butoxy groups, can berecited.

As the alkoxycarbonyl group, methoxycarbonyl and ethoxycarbonyl groupscan be recited.

As the acyl group, formyl, acetyl and benzoyl groups can be recited. Asthe acyloxy group, acetoxy and butyryloxy groups can be recited.

Typical examples of a structure represented by A₀, namely a polycyclicor monocyclic type of alicyclic moiety in the poly- ormonocycloaliphatic group, are illustrated below.

The formula (XV) is explained next.

n in formula (XV) is 0 or 1.

Xa and Xb each represent a hydrogen atom or an alkyl group having 1 to 4carbon atoms.

Ya and Yb represents a hydrogen atom, a hydroxyl group or a grouprepresented by —COOXc. Herein, Xc is a hydrogen atom or an alkyl groupin one mode.

Examples of such an alkyl group include alkyl groups having 1 to 8carbon atoms, preferably alkyl groups having 1 to 4 carbon atoms, suchas methyl, ethyl, propyl, butyl and tert-butyl groups. Further, part orall of hydrogen atoms of those alkyl groups each may be replaced withhydroxyl group(s), halogen atom(s) or cyano group(s).

In another mode, Xc represents a constituent of the group —COOXc whichfunctions as an acid-decomposable group in its entity. As examples ofsuch Xc, mention may be made of groups represented by the foregoingformula (x) or (y). In the other mode, Xc may be a group containing anacid-decomposable lactone structure or a group containing anacid-decoomposable alicyclic structure.

Resins obtained by copolymerizing repeating units of formula (XV) andmaleic anhydride, and resins obtained by copolymerizing repeating unitsof formula (XV), maleic anhydride and acrylates or methacrylates arealso preferred as the resins used in the invention.

Examples of repeating structural units represented by formulae (XII) to(XV) respectively are illustrated below, but these examples should notbe construed as limiting the scope of the invention.

Of these examples, the repeating units (b1), (b2), (b5), (b9), (b47),(b48), (b49), (b50), (b54) (b58) and (b60) are preferred over the othersbecause they are generally decomposable with acids. In particular, therepeating units (b1), (b47), (b48) and (b49), wherein an adamantyl groupis attached to the resin main chain via an acid-decomposable structure,are preferable over the others. The use of these repeating units canensure improvements in dry etching resistance and resolution.

In the acid-decomposable resins as described above, carboxyl groups canfurther be contained.

These carboxyl groups may be introduced in repeating structural units asrecited above or other repeating structural units.

Additionally, the carboxyl groups may be introduced at two or morepositions of each structural unit.

The suitable content of all carboxyl group-containing repeatingstructural units in an acid-decomposable resin comprised in the presentpositive photosensitive composition, though adjusted depending on thedesired properties including alkali developability, adhesion to asubstrate and sensitivity, is from 0 to 60 mole %, preferably from 0 to40%, particularly preferably from 0 to 20 mole %, of the total repeatingstructural units of the acid-decomposable resin.

Examples of a repeating structural unit containing a carboxyl group areillustrated below, but the invention should not be construed as beinglimited to these examples.

For performance improvement of an acid-decomposable resin, otherpolymerizable monomers may be introduced into the resin bycopolymerization so far as the introduction thereof does not noticeablyimpair the resin's transparency at wavelengths below 220 nm and dryetching resistance.

Copolymerizable monomers usable for the foregoing purpose are compoundscontaining one addition polymerizable unsaturated bond per molecule,which can be selected from acrylic acid esters, acrylamides, methacrylicacid esters, methacrylamides, allyl compounds, vinyl ethers, vinylesters, styrenes or crotonic acid esters.

More specifically, the acrylic acid esters include, e.g., alkylacrylates (preferably having 1-10C alkyl moieties), such as methylacrylate, ethyl acrylate, propyl acrylate, t-butyl acrylate, amylacrylate, cyclohexyl acrylate, ethylhexyl acrylate, octyl acrylate,t-octyl acrylate, chloroethyl acrylate, 2-hydroxyethyl acrylate,2,2-dimethylhydroxypropyl acrylate, 5-hydroxypentyl acrylate,trimethylolpropane monoacrylate, pentaerythritol monoacrylate, glycidylacrylate, benzyl acrylate, methoxybenzyl acrylate, furfuryl acrylate andtetrahydrofurfuryl acrylate, aryl acrylates and methoxyethoxyethylacrylate.

The methacrylic acid esters include, e.g., alkyl methacrylates(preferably having 1-10C alkyl moieties), such as methyl methacrylatae,ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, t-butylmethacrylate, amyl methacrylate, hexyl methacrylate, cyclohexylmethacrylatae, benzyl methacrylate, octyl methacrylate, 2-hydroxyethylmethacrylate, 4-hydroxybutyl methacrylate, 5-hydroxypentyl methacrylate,2,2,-dimethyl-3-hydroxypropyl methacrylate, trimethylolpropanemonomethacrylate, pentaerythritol monomethacrylate, glycidylmethacrylate, furfuryl methacrylate and tetrahydrofurfuryl methacrylate,aryl methacrylates (e.g., phenyl methacrylate, naphthyl methacrylate),and methoxyethoxyethyl methacrylate.

The acrylamides include, e.g., acrylamide, N-alkylacrylamides(preferably having 1-10C alkyl moieties, such as methyl, ethyl, propyl,butyl, t-butyl, heptyl, octyl, cyclohexyl, benzyl and hydroxyethyl),N-arylacrylamides, N,N-dialkylacrylamides (preferably having 1-10C alkylmoieties, such as methyl, ethyl, butyl, isobutyl, ethylhexyl andcyclohexyl), N,N-diacrylacrylamides, N-hydroxyethyl-N-methylacrylamide,and N-2-acetamidoethyl-N-acetylacrylamide.

The methacrylamides include, e.g., methacrylamide,N-alkylmethacrylamides (preferably having 1-10C alkyl moieties, such asmethyl, ethyl, t-butyl, ethylhexyl, hydroxyethyl and cyclohexyl),N-acrylmethacrylamides, N,N-dialkylmethacrylamides (the alkyl moietiesof which are, e.g., ethyl, propyl or butyl groups),

-   N-hydroxyethyl-N-methylmethacrylamide,-   N-methyl-N-phenylmethacrylamide, and-   N-ethyl-N-phenylmethacrylamide.

The allyl compounds include, e.g., allyl esters (such as allyl acetate,allyl caproate, allyl lurate, allyl palmitate, allyl stearate, allylbenzoate, allyl acetoacetate and allyl lactate), and allyloxyethanol.

The crotonic acid esters include, e.g., alkyl crotonates (such as butylcrotonate, hexyl crotonate and glycerol monocrotonate), and the itaconicacid esters include, e.g., dialkyl itaconates (such as dimethylitaconate, diethyl itaconate and dibutyl itaconate).

Further, copolymerizable monomers usable herein include dialkyl estersof maleic or fumaric acid (e.g., dimethyl maleate and dibutyl fumarate),maleic anhydride, maleimide, acrylonitrile, methacrylonitrile andmaleylonitrile.

And besides, any of addition polymerizable unsaturated compounds may begenerally used as comonomers.

Of the compounds recited above, methoxyethoxyethyl methacrylate andmethoxyethoxyethyl acrylate are particularly preferred over the others.

The suitable content of the repeating structural units derived fromother polymerizable monomers in the acid-decomposable resin (B) is notmore than 50 mole %, preferably not more than 30 mole %, of the totalrepeating structural units.

In view of securing transparency to any of actinic rays or radiation, itis desirable that no aromatic rings be contained in theacid-decomposable resin (B). This is because it is difficult to allowirradiated rays to reach the bottom of resist film when the transparencyto the irradiated rays is lowered by the introduction of aromatic rings;as a result, the resist comes to have the so-called tapered patternprofile.

The suitable content of the acid-decomposable group-containing repeatingstructural units in the acid-decomposable resin (B), though adjusted soas to attain a proper balance between dry etching resistance and alkalidevelopability, is at least 10 mole %, preferably at least 15 mole %,particularly preferably at least 20 mole %, of the total repeatingstructural units.

The suitable content of the alicyclic group-containing structural units(preferably the repeating structural units of formulae (XII) to (XIV))in the acid-decomposable resin (B) is at least 20 mole % of the totalrepeating structural units although it is also adjusted so as to attaina proper balance between dry etching resistance and alkalidevelopability. Further, it is preferable that the foregoing content isin the range of 30 to 80 mole %, preferably 35 to 70 mole %,particularly preferably 40 to 60 mole %, of the total repeatingstructural units.

The suitable content of the lactone structure-containing structuralunits in the acid-decomposable resin (B) is also adjusted so as toattain a proper balance between dry etching resistance and alkalidevelopability. Specifically, it is at least 5 mole %, preferably atleast 10 mole %, particularly at least 20 mole %, of the total repeatingstructural units.

The suitable weight average molecular weight of the acid-decomposableresin (B) is from 1,000 to 100,000, preferably from 2,000 to 50,000,particularly preferably from 3,000 to 30,000, as measured by GPC andcalculated in terms of polystyrene. And the suitable dispersion degreeof the acid-decomposable resin (B) is from 1.0 to 5.0, preferably from1.0 to 3.0.

In each of the present compositions, the suitable proportion of theresin (B) capable of increasing its solubility in an alkali developerunder the action of an acid is from 20 to 99.8 weight %, preferably from50 to 99.5 weight %, on a solids basis.

<<(C) Compound Having Molecular Weight of No Greater than 3,000 andCapable of Decomposing Under Action of Acid to Increase its Solubilityin Alkali Developer (Component (C))>>

The compound as Component (C) is contained as an essential component inthe second composition, but it may be mixed in the first composition, ifdesired. The Component (C) is a low molecular compound containing one ormore of an acid-decomposable group and capable of increasing itssolubility in an alkali developer under the action of an acid. Themolecular weight of such a compound is not higher than 3,000, preferablyfrom 200 to 2,000, particularly preferably from 300 to 1,500. TheComponent (C) functions as an inhibitor against dissolving unexposedareas in an alkali developer. Additionally, the term “acid-decomposabledissolution inhibiting compound” in the following description has thesame meaning as Component (C).

Similarly to the foregoing resin (B), it is preferable in the inventionthat the compound (C) be selected properly depending on the kind of theexposure light or the irradiation ray. Specifically, it is desired thatthe type of compound (C) be selected in view of transparency andsensitivity to exposure light or irradiation ray, and further dryetching resistance.

Examples of a compound (C) used suitably in a photosensitive compositionto undergo exposure to KrF excimer laser or irradiation with electronbeams or X-ray include polyhydroxy compounds protected byacid-decomposable groups.

Examples of a compound (C) used preferably in a photosensitivecomposition to undergo exposure to ArF excimer laser include compoundscontaining no aromatic rings but containing acid-decomposable groups andalicyclic structures.

Compounds used suitably as compound (C) in photosensitive compositionsto undergo exposure to ArF excimer laser are illustrated below indetail.

From the viewpoint of causing no decrease in transparency to radiationof 220 nm or below, acid-decomposable group-containing alicyclic oraliphatic compounds, such as cholic acid derivatives containingacid-decomposable groups as described in Proceeding of SPIE, 2724, 355(1996), are suitable as acid-decomposable dissolution-inhibitingcompounds (C). With respect to the acid-decomposable groups andalicyclic structures contained in those compounds, the same ones asrecited in the description of the acid-decomposable resins can berecited as examples thereof.

Examples of an acid-decomposable dissolution-inhibiting compound (C) areillustrated below, but the invention should not be construed as beinglimited to these compounds.

Compounds (C) suitably used in photosensitive compositions to undergoexposure to KrF excimer laser, irradiation with electron beams orirradiation with X-ray are illustrated below in detail.

It is preferable that Component (C), or an acid-decomposabledissolution-inhibiting compound, contain at least two acid-decomposablegroups in a condition that at least 8 atoms linked one after another,excluding the atoms constituting the acid-decomposable groups, intervenebetween the acid-decomposable groups located at the greatest distancefrom each other.

The acid-decomposable dissolution-inhibiting compounds preferred in theinvention are:

(a) compounds containing in each of their structures at least twoacid-decomposable groups in a condition that at least 10 atoms,preferably at least 11 atoms, particularly preferably at least 12 atoms,which are linked one after another, excluding the atoms constituting theacid-decomposable groups, intervene between the acid-decomposable groupslocated at the greatest distance from each other, and

(b) compounds containing in each of their structures at least threeacid-decomposable groups in a condition that at least 9 atoms,preferably at least 10 atoms, particularly preferably at least 11 atoms,which are linked one after another, excluding the atoms constituting theacid-decomposable groups, intervene between the acid-decomposable groupslocated at the greatest distance from each other.

Further, it is preferable that the upper limit of the number of atomsintervening between the acid-decomposable groups be 50, preferably 30.

When the acid-decomposable dissolution-inhibiting compound contains atleast 3, preferably at least 4, acid-decomposable groups, and even whenit contains 2 acid-decomposable groups, they can have markedly improvedinhibition capabilities against dissolving alkali-soluble resins as longas the acid-decomposable groups are located at a certain distance orgreater.

Additionally, the distance between acid-decomposable groups is expressedin terms of the number of linked atoms intervening between them,excluding the atoms constituting the acid-decomposable groups. Forinstance, in the case of the following compounds (1) and (2) each, thedistance between the acid-decomposable groups is 4 linked atoms, whileit is 12 linked atoms in the case of the following compound (3).

A⁰-OOC—¹CH₂—²CH₂—³CH₂—⁴CH₂—COO-A⁰  (2)

(acid-decomposable groups: —COO-A⁰ and —O—B⁰)

The acid-decomposable dissolution-inhibiting compounds preferred in theinvention, though may have a plurality of acid-decomposable groups onone benzene ring, are each comprised of a skeleton wherein oneacid-decomposable group is present on one benzene ring.

Examples of a group capable of being decomposed by an acid, namely agroup containing a —COO-A⁰ or —O—B⁰ group, include —R⁰—COO-A⁰ and—Ar—O—B⁰ groups.

Herein, A⁰ represents a —C(R⁰¹)(R⁰²)(R⁰³), —Si(R⁰¹)(R⁰²)(R⁰³) or—C(R⁰⁴)(R⁰⁵)—O—R⁰⁶ group. B⁰ represents A⁰ or a —CO—O-A⁰ group.

R⁰¹, R⁰², R⁰³, R⁰⁴ and R⁰⁵, which are the same or different, eachrepresent a hydrogen atom, an alkyl group, a cycloalkyl group, analkenyl group or an aryl group. R⁰⁶ represents an alkyl group or an arylgroup. Herein, however, at least two among R⁰¹ to R⁰³ groups are groupsother than hydrogen, and any two among R⁰¹ to R⁰³ groups or any twoamong R⁰⁴ to R⁰⁶ groups may combine with each other to form a ring. R⁰represents a divalent or higher aliphatic or aromatic hydrocarbon groupwhich may have a substituent, and Ar represents a divalent or highermonocyclic or polycyclic aromatic group which may have a substituent.

Herein, it is preferable for the alkyl group to be a 1-4C alkyl group,such as methyl, ethyl, propyl, n-butyl, sec-butyl or t-butyl group, forthe cycloalkyl group to be a 3-10C cycloalkyl group, such ascyclopropyl, cyclobutyl, cylohexyl or adamantyl group, for the alkenylgroup to be a 2-4C alkenyl group, such as vinyl, propenyl, allyl orbutenyl group, and for the aryl group to be a 6-14C aryl group, such asphenyl, xylyl, toluoyl, cumenyl, naphthyl or anthracenyl group.

As examples of substituents the groups represented by R⁰ and —Ar— mayhave, mention may be made of a hydroxyl group, a halogen atom (e.g.,fluorine, chlorine, bromine, iodine), a nitro group, a cyano group, analkyl group as recited above, an alkoxy group such as methoxy, ethoxy,hydroxyethoxy, propoxy, hydroxypropoxy, n-butoxy, isobutoxy, sec-butoxyor t-butoxy group, an alkoxycarbonyl group such as methoxycarbonyl orethoxycarbonyl group, an aralkyl group such as benzyl, phenetyl or cumylgroup, an aralkyloxy group, an acyl group such as formyl, acetyl,butyryl, benzoyl, cinnamyl or valeryl group, an acyloxy group such asbutryloxy group, an alkenyl group as recited above, an alkenyloxy groupsuch as vinyloxy, propenyloxy, allyloxy or butenyloxy group, an arylgroup as recited above, an aryloxy group such as phenoxy group, and anaryloxycarbonyl group such as benzoyloxy group.

As suitable examples of an acid-decomposable group, mention may be madeof a silyl ether group, a cumyl ester group, an acetal group, atetrahydropyranyl ether group, an enol ether group, an enol ester group,a tertiary alkyl ether group, a tertiary alkyl ester group, and atertiary alkyl carbonate group. Of these groups, a tertiary alkyl estergroup, a tertiary alkyl carbonate group, a cumyl ester group and atetrahydropyranyl ether group are preferred over the others.

Suitable examples of Component (C) include compounds prepared byprotecting a part or all of phenolic OH groups contained in thepolyhydroxy compounds as disclosed in JP-A-1-289946, JP-A-1-289947,JP-A-2-2560, JP-A-3-128959, JP-A-3-158855, JP-A-3-179353, JP-A-3-191351,JP-A-3-200251, JP-A-3-200252, JP-A-3-200253, JP-A-3-200254,JP-A-3-200255, JP-A-3-259149, JP-A-3-279958, JP-A-3-279959, JP-A-4-1650,JP-A-4-1651, JP-A-4-11260, JP-A-4-12356, JP-A-4-12357, and JapanesePatent Application Nos. 3-33229, 3-230790, 3-320438, 4-25157, 4-52732,4-103215, 4-104542, 4-107885, 4-107889 and 4-152195 with the —R⁰—COO-A⁰or B⁰ groups described above.

Of these compounds, the compounds prepared from the polyhydroxycompounds disclosed in JP-A-1-289946, JP-A-3-128959, JP-A-3-158855,JP-A-3-179353, JP-A-3-200251, JP-A-3-200252, JP-A-3-200255,JP-A-3-259149, JP-A-3-279958, JP-A-4-1650, JP-A-4-11260, JP-A-4-12356,JP-A-4-12357, and Japanese Patent Application Nos. 4-25157, 4-103215,4-104542, 4-107885, 4-107889 and 4-152195 are preferred over the others.

Examples of skeletons of compounds preferred as Component (C) in theinvention are illustrated below.

Each of R groups in Compounds (1) to (44) represents a hydrogen atom,

Therein, at least two R groups in each compound, or three R groupsdepending on the compound structure, are groups other than hydrogen, andR groups in each compound may be the same or different.

In the first composition, the suitable proportion of Component (C) isfrom 3 to 45 weight %, preferably from 5 to 30 weight %, particularlypreferably from 10 to 20 weight %, based on the total solids therein.

In the second composition also, the suitable proportion range ofComponent (C) is the same as in the first composition.

<<(D) Alkali-Soluble Resin (Component (D))>>

An alkali-soluble resin (D) is an essential component in the secondcomposition. And it may be mixed in the first composition, if desired.The alkali-soluble resin (D) is a resin insoluble in water but solublein an alkali developer, and used for adjusting the alkali solubility ofthe second composition. Such a resin contains no acid-decomposablegroups in a substantial sense.

Similarly to the foregoing resin (B), it is preferable in the inventionthat the resin (D) be selected properly depending on the kind of theexposure light or the irradiation ray. Specifically, it is desired thatthe type of the resin (D) be selected in view of transparency andsensitivity to exposure light or irradiation ray, and further dryetching resistance.

Examples of a resin (D) used suitably in a photosensitive composition toundergo exposure to KrF excimer laser or irradiation with electron beamsor X-ray include resins having alkali-soluble groups (such aspoly(hydroxystyrene) resins)

Examples of a resin (D) used preferably in a photosensitive compositionto undergo exposure to ArF excimer laser include resins containing noaromatic rings but containing alkali-soluble groups.

Resins which can be suitably used as resin (D) in photosensitivecompositions to undergo exposure to ArF excimer laser are illustratedbelow in detail.

Such resins can include novolak resins whose molecular weights are inthe range of about 1,000 to 20,000 and poly(hydroxystyrene) derivativeswhose molecular weights are in the range of about 3,000 to 50,000, butthese resins each show a great absorption peak at a wavelength of 250 nmor below. Therefore, it is preferable that they be used after undergopartial hydrogenation or in a proportion of no higher than 30 weight %to the total resins used.

In addition, resins containing carboxyl groups as alkali-soluble groupscan be used, too. From the viewpoint of enhancing dry etchingresistance, it is desirable for those resins to contain mono- orpolycycloaliphatic groups. Specifically, such resins include a copolymerof a methacrylic acid ester having a cycloaliphatic structure showing noacid-decomposability and (meth)acrylic acid, and a resin prepared from aterminal carboxyl group-containing alicyclic ester of (meth)acrylicacid.

Resins which can be suitably used as resin (D) in photosensitivecompositions to undergo exposure to KrF excimer laser, or irradiationwith electron beams or X-ray are described below in detail.

Examples of resins usable as Component (D) include novolak resin,hydrogenated novolak resin, acetone-pyrogallol resin,poly(o-hydroxystyrene), poly(m-hydroxystyrene), poly(p-hydroxystyrene),hydrogenated poly(hydroxystyrene), poly(halogen- or alkyl-substitutedhydroxystyrene), copolymer of hydroxystyrene and N-substitutedmaleimide, copolymer of o/p-hydroxystyrene and m/p-hydroxystyrene,poly(hydroxystyrene) whose hydroxyl groups are partially O-alkylated(e.g., O-methylated, O-(1-methoxy)ethylated, O-(1-ethoxy)ethylated,O-2-tetrahydropyranylated, or O-(t-butoxycarbonyl)methylated in aproportion of 5 to 30 mole %) or O-acylated (e.g., O-acetylated orO-(t-butoxy)carbonylated in a proportion of 5 to 30 mole %),styrene-maleic anhydride copolymer, styrene-hydroxystyrene copolymer,α-methylstyrene-hydroxystyrene copolymer, carboxyl group-containingmethacrylate resin and derivatives thereof, and polyvinyl alcoholderivatives. However, these examples should not be construed as limitingthe scope of the invention.

Of these alkali-soluble resins as resin (D), novolak resin,poly(o-hydroxystyrene), poly(m-hydroxystyrene), poly(p-hydroxystyrene)and copolymers of o-, m- and p-hydroxystyrenes, an alkyl-substitutedpoly(hydroxystyrene), partially O-alkylated or O-acylatedpoly(hydroxystyrene), styrene-hydroxystyrene copolymer andα-methylstyrene-hydroxystyrene copolymer are preferred over the others.The novolak resin can be synthesized by subjecting specified monomers asmain components and aldehydes to addition condensation reaction in thepresence of an acid catalyst.

The suitable weight average molecular weight of novolak resin is from1,000 to 30,000. When the weight average molecular weight is lower than1,000, great reduction in resist film thickness is caused inunirradiated areas by development. The weight average molecular weighthigher than 30,000, on the other hand, becomes a cause of a decrease indeveloping speed. The especially suitable range is from 2,000 to 20,000,

Further, the weight average molecular weight of resins other thannovolak resin, such as the poly(hydroxystyrene) and derivatives thereofand copolymers as recited above, is not lower than 2,000, preferablyfrom 5,000 to 200,000, particularly preferably from 8,000 to 100,000.From the viewpoint of improving heat resistance of the resist film, itis preferable that the resin as recited above has a weight averagemolecular weight of no lower than 10,000.

Herein, the weight average molecular weight is defined as the valuemeasured by GPC and calculated in terms of polystyrene.

The alkali-soluble resins as recited above may be used as a mixture oftwo or more thereof.

The suitable proportion of alkali-soluble resins used is from 40 to 97weight %, preferably from 60 to 90 weight %, based on the total solidsin the second composition.

<<(E) Nitrogen-Containing Basic Compound>>

In order to reduce a change in performance due to time passage fromexposure to baking, it is desirable for the present positivephotosensitive compositions to contain nitrogen-containing basiccompounds.

Such basic compounds are preferably represented by the followingstructural formulae (A) to (E).

In the above formula (A), R²⁵⁰, R²⁵¹ and R²⁵² each independentlyrepresent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, anaminoalkyl group having 1 to 6 carbon atoms, a hydroxyalkyl group having1 to 6 carbon atoms, or a substituted or unsubstituted aryl group having6 to 20 carbon atoms. Further, R²⁵⁰ and R²⁵¹ may combine with each otherto form a ring.

In the above formula, R²⁵³, R²⁵⁴, R²⁵⁵ and R²⁵⁶ each independentlyrepresent an alkyl group having 1 to 6 carbon atoms.

Suitable examples of such basic compounds include substituted orunsubstituted guanidine, substituted or unsubstituted aminopyridine,substituted or unsubstituted aminoalkylpyridine, substituted orunsubstituted aminopyrrolidine, substituted or unsubstituted indazole,substituted or unsubstituted pyrazole, substituted or unsubstitutedpyrazine, substituted or unsubstituted pyrimidine, substituted orunsubstituted purine, substituted or unsubstituted imidazoline,substituted or unsubstituted pyrazoline, substituted or unsubstitutedpiperazine, substituted or unsubstituted aminomorpholine, substituted orunsubstituted aminoalkylmorpholine, mono-, di- and tri-alkylamines,substituted or unsubstituted aniline, substituted or unsubstitutedpiperidine, and mono- or di-ethanolamine. As examples of substituentsthe above-recited compounds can have preferably, mention may be made ofan amino group, an aminoalkyl group, an alkylamino group, an aminoarylgroup, an arylamino group, an alkyl group, an alkoxy group, an acylgroup, an acyloxy group, an aryl group, an aryloxy group, a nitro group,a hydroxyl group and a cyano group.

Specific examples of basic compounds preferred in particular includeguanidine, 1,1-dimethylguanidine, 1,1,3,3,-tetramethylguanidine,2-aminopyridine, 3-aminopyridine, 4-aminopyridine,2-dimethylaminopyridine, 4-dimethylaminopyridine,2-diethylaminopyridine, 2-(aminomethyl)pyridine,2-amino-3-methylpyridine, 2-amino-4-methylpyridine,2-amino-5-methylpyridine, 2-amino-6-methylpyridine,3-aminoethylpyridine, 4-aminoethylpyridine, 3-aminopyrrolidine,piperazine, N-(2-aminoethyl)piperazine, N-(2-aminoethyl)piperidine,4-amino-2,2,6,6-tetramethylpiperidine, 4-piperidinoppiperidine,2-iminopiperidine, 1-(2-aminoethyl)pyrrolidine, pyrazole,3-amino-5-methylpyrazole, 5-amino-3-methyl-1-p-tolylpyrazole, pyrazine,2-(aminomethyl)-5-methylpyrazine, pyrimidine, 2,4-diaminopyrimidine,4,6-dihydroxypyrimidine, 2-pyrazoline, 3-pyrazoline, N-aminomorpholine,N-(2-aminoethyl)morpholine, 1,5-diazobicyclo[4.3.0]nona-5-ene,1,8-diazabicyclo[5.4.0]undeca-7-ene, 2,4,5-triphenylimidazole,tri(n-butyl)amine, tri(n-octyl)amine, N-phenyldiethanolamine,N-hydroxyethylpiperidine, 2,6-diisoproopylaniline andN-cyclohexyl-N′-morpholinoethylthiourea. However, these examples shouldnot be construed as limiting the scope of the invention.

These nitrogen-containing basic compounds (E) may be used alone or asmixtures of two or more thereof. The proportion of nitrogen-containingbasic compounds used is generally from 0.001 to 10 weight %, preferablyfrom 0.01 to 5 weight %, based on the total solids in the photosensitiveresin composition. The effect of the foregoing nitrogen-containing basiccompounds cannot be produced when the compounds are added in aproportion lower than 0.001 weight %; while the addition in a proportionhigher than 10 weight % may cause a decrease in sensitivity anddeterioration of developability in the unexposed areas.

<<(F) Surfactant Containing Either Fluorine or Silicon Atom, or BothFluorine and Silicone Atoms>>

It is preferable for the present positive photosensitive resincompositions each to contain a surfactant containing at least onefluorine atom, a surfactant containing at least one silicon atom, or asurfactant containing both fluorine and silicon atoms. Also, any two ormore of these surfactants may be contained as a mixture.

When the light source of 250 nm or below, especially 220 nm or below, isused for exposure, the present positive photosensitive compositions eachcan have satisfactory sensitivity and resolution by containing theforegoing surfactant (s) as Component (F) and can provide resistpatterns having a good adhesion and reduced in development defects.

As examples of such surfactants, mention may be made of the surfactantsdisclosed in JP-A-62-36663, JP-A-61-226746, JP-A-61-226745,JP-A-62-170950, JP-A-63-34540, JP-A-7-230165, JP-A-8-62834,JP-A-9-54432, JP-A-9-5988, and U.S. Pat. Nos. 5,405,720, 5,360,692,5,529,881, 5,296,330, 5,436,098, 5,576,143, 5,294,511 and 5,824,451.Further, the commercially available surfactants as recited below canalso be used as they are.

Examples of commercial surfactants usable in the invention includefluorine-containing surfactants, such as Eftop EF301, EF303(manufactured by Shin-Akita Kasei K.K.), Florad FC430, FC431(manufactured by Sumitomo 3M, Inc.), Megafac F171, F173, F176, F189, R08(manufactured by Dainippon Ink & Chemicals, Inc.), Surflon S-382, SC101,SC102, SC103, SC104, SC105, SC106 (manufactured by Asahi Glass Co.,Ltd.) and Troysol S-366 (manufactured by Troy Chemical Industries,Inc.), and silicon-containing surfactants, such as polysiloxane polymerKP-341 (manufactured by Shin-Etsu Chemical Industry Co., Ltd.).

The suitable proportion of surfactants used is from 0.0001 to 2 weight%, preferably from 0.001 to 1 weight %, based on the total solids in thepositive photosensitive resin composition.

<<Other Substances>>

In the present positive photosensitive compositions, dyes, plasticizers,surfactants other than the foregoing Component (F), photosensitizers,and compounds for promoting solubility in a developer may further becontained.

The compounds for promoting solubility in a developer which can be usedin the invention are low molecular compounds containing at least two permolecule of phenolic OH groups, or containing at least one per moleculeof carboxyl group. When they are used in the compositions suitable forArF exposure, it is preferable for them to be carboxyl group-containingalicyclic or aliphatic compounds.

The suitable proportion of these dissolution-promoting compounds is from2 to 50 weight %, preferably from 5 to 30 weight %, to the resin (B)capable of decomposing under the action of acid to increase thesolubility in an alkali developer. Those compounds added in a proportiongreater than 50 weight % give rise to aggravation of development residueand a new defect that patterns are deformed at the time of development.

On the other hand, the compounds containing at least two phenolic OHgroups per molecule have suitability for KrF exposure, or electron-beamor X-ray irradiation. And they are preferably phenolic compounds havinga molecular weight of no higher than 1,000. Although these compounds arerequired to have at least two phenolic OH groups per molecule,development latitude improving effect is lost when the number ofphenolic OH groups in a molecule exceeds 10. Further, in the cases wherethe ratio of the number of phenolic OH groups to the number of aromaticrings is smaller than 0.5, film-thickness dependence is great anddevelopment latitude may become narrow. On the other hand, when theforegoing ratio is greater than 1.4, the stability of the composition isdegraded, and it becomes difficult to achieve high resolution andsatisfactory film-thickness dependence.

Those phenolic compounds whose molecular weights are not higher than1,000 can be synthesized easily by reference to the methods as describedin JP-A-4-122938, JP-A-23-28531, U.S. Pat. No. 4,916,210 and EuropeanPatent 2,192,294.

Examples of such phenolic compounds include those recited below, but thecompounds usable in the invention should not be construed as beinglimited to these examples.

Namely, the phenolic compounds usable in the invention includeresorcinol, phloroglucine, 2,3,4-trihydroxybenzophenone,2,3,4,4′-tetrahydroxybenzophenone,2,3,4,3′,4′,5′-hexahydroxybenzophenone, acetone-pyrogallol condensationresin, phloroglucoside, 2,4,2′,4′-biphenyltetraol,4,4′-thiobis(1,3-dihydroxy)benzene, 2,2′,4,4′,-tetrahydroxydiphenylether, 2,2′,4,4′-tetrahydroxydiphenyl sulfoxide,2,2′,4,4′-tetrahydroxydiphenyl sulfone, tris(4-hydroxyphenyl)methane,1,1-bis(4-hydroxyphenyl)cyclohexane, 4,4-(α-methylbenzylidene)bisphenol,α,α′,α″-tris(4-hydroxyphenyl)-1,3,5-triisopropylbenzene,α,α′,α″-tris(4-hydroxyphenyl)-1-ethyl-4-isopropylbenzene,1,2,2-tris(hydroxyphenyl)propane,1,1,2-tris(3,5-dimethyl-4-hydroxyphenyl)propane,2,2,5,5-tetrakis(4-hydroxyphenyl)hexane,1,2-tetrakis(4-hydroxyphenyl)ethane, 1,1,3-tris(hydroxyphenyl)butane,and para[α,α,α′,α′-tetrakis(4-hydroxyphenyl)]xylene.

Examples of carboxyl group-containing alicyclic and aliphatic compoundsinclude carboxylic acid derivatives having steroid structures, such ascholic acid, deoxycholic acid and lithocholic acid, adamantanecarboxylicacid derivatives, adamantanedicarboxylic acid, cyclohexanecarboxylicacid, and cyclohexanedicarboxylic acid. However, these examples shouldnot be construed as limiting the scope of the invention.

To the present compositions, surfactants other than the foregoingfluorine- and/or silicon-containing surfactants (F) can also be added.Examples of surfactants which can be added include nonionic surfactants,such as polyoxyethylene alkyl ethers (e.g., polyoxyethylene laurylether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether,polyoxyethylene oleyl ether), polyoxyethylene alkyl aryl ethers (e.g.,polyoxyethylene octyl phenol ether, polyoxyethylene nonyl phenyl ether),polyoxyethylene-polyoxypropylene block copolymers, sorbitan fatty acidesters (e.g., sorbitan monolaurate, sorbitan monopalmitate, sorbitanmonostearate, sorbitan monooleate, sorbitan trioleate, sorbitantristearate), and polyoxyethylenesorbitan fatty acid esters (e.g.,polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitanmonopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylenesorbitan trioleate, polyoxyethylene sorbitan tristearate).

These surfactants may be added alone, or some of them can be added ascombinations.

<<Use of Present Composition>>

Each of the present photosensitive compositions is a solution preparedby mixing the ingredients mentioned above in a proper solvent, and usedin a state of being coated on a specified support. Examples of a solventsuitably used herein include ethylene dichloride, cyclohexanone,cyclopentanone, 2-heptanone, γ-butyrolactone, methyl ethyl ketone,ethylene glycol monomethyl ether, ethylene glycol monoethyl ether,2-methoxyethylacetate, ethylene glycolmonoethyl ether acetate, propyleneglycol monomethyl ether, propylene glycol monomethyl ether acetate,toluene, ethyl acetate, methyl lactate, ethyl lactate, methylmethoxypropionate, ethyl ethoxypropionate, methyl pyruvate, ethylpyruvate, propyl pyruvate, N,N-dimethylformamide, dimethyl sulfoxide,N-methylpyrrolidone, and tetrahydrofuran. These solvents are used aloneor as mixtures.

Of the solvents recited above, cyclohexanone, 2-heptanone, propyleneglycol monomethyl ether acetate, propylene glycol monomethyl ether,ethyl lactate and ethyl ethoxypropionate are preferred over the others,and these solvents may be used alone or as a 1:9 to 9:1 mixture of anytwo of them.

The positive photosensitive composition dissolved in a solvent is coatedon a specified substrate in the following manner.

Namely, the photosensitive composition is coated on a substrate (e.g.,silicon/silicon dioxide coating) as used for production ofprecision-integrated circuit elements by means of an appropriate coatingmachine, such as a spinner or a coater.

After coating, the photosensitive composition is subjected to exposureto light via the desired mask, baking and then development. Thus, it canprovide resist patterns of good quality. In the exposure to light, farultraviolet rays having wavelengths of 250 nm or below, preferably 220nm or below, are used to advantage. More specifically, it is preferablefor the exposure light to be KrF excimer laser (248 nm), ArF excimerlaser (193 nm), F2 excimer laser (157 nm), X-ray or electron beams canbe used as exposure light.

The developer used in subjecting the present photosensitive compositionto development-processing may be an aqueous alkaline solution containingan inorganic alkali such as sodium hydroxide, potassium hydroxide,sodium carbonate, sodium silicate, sodium metasilicate or aqueousammonia, a primary amine such as ethylamine or n-propylamine, asecondary amine such as diethylamine or di-n-butylamine, a tertiaryamine such as triethylamine or methyldiethylamine, an alcoholamine suchas dimethylethanolamine or triethanolamine, a quaternary ammonium saltsuch as tetramethylammonium hydroxide or tetraethylammonium hydroxide,or a cyclic amine such as pyrrole or piperidine.

To the aqueous alkaline solution, alcohol and surfactants may further beadded in preferable amounts.

The invention will now be illustrated in more detail by reference to thefollowing examples, but these examples should not be construed aslimiting the scope of the invention in any way.

SYNTHESIS EXAMPLE 1 Synthesis of Sulfonic Acid Generator as Component(A) <(1) Synthesis of Compound I-1>

To 20 g of bis(t-butylphenyl) iodonium iodide were added 500 ml ofmethanol and 8.9 g of silver oxide (I). This admixture was placed in adark room and stirred for 4 hours at room temperature. The resultingreaction solution was filtered sequentially with filter paper and a0.1-μm filter, thereby removing the silver compound. The filtrate wasmixed with 12.1 g of perfluoroethoxyethanesulfonic acid, andconcentrated. The thus obtained oily matter was dissolved in 1-liter ofethyl acetate, and washed twice with a 2% aqueous solution oftetramethylammonium hydroxide and further twice with distilled water.The organic layer was dried and concentrated to yield 48 g of CompoundI-1.

300 MHz ¹H-NMR (CDCl₃)

δ 0.6 (t, 6H), δ 1.15 (s, 12H), δ 1.55 (q, 4H), δ 7.3 (d, 4H), δ 7.8 (d,4H)

Compounds (I-2) to (I-9) were also synthesized using the correspondingsulfonium iodides respectively in accordance with the same method asdescribed above.

<(2) Synthesis of Compound II-1>

Triphenylsulfonium iodide in an amount of 28.1 g was added 500 ml ofmethanol, and thereto was added 17.3 g of silver oxide (I). Thisadmixture was placed in a dark room and stirred for 4 hours at roomtemperature. The resulting reaction solution was filtered sequentiallywith filter paper and a 0.1-μm filter, thereby removing the silvercompound. The filtrate was mixed with 25 g ofperfluoroethoxyethanesulfonic acid, and concentrated. The thus obtainedoily matter was dissolved in 1-liter of ethyl acetate, and washed twicewith a 2% aqueous solution of tetramethylammonium hydroxide and furthertwice with distilled water. The organic layer was dried andconcentrated, and the solid obtained was washed with diisopropyl etherto yield 48 g of Compound II-1.

300 MHz ¹H-NMR

δ 7.5-7.7 (m, 15H)

Compounds (II-2) to (II-16) were also synthesized using thecorresponding sulfonium iodides respectively in accordance with the samemethod as described above.

Further, compounds represented by formula (III) were synthesized usingthe same method as the compounds of formula (II).

SYNTHESIS EXAMPLE 2 Synthesis of Resin as Component (B))

<(1) Synthesis of p-(1-(Cyclohexylethoxy)ethoxy)styrene/p-Hydroxystyrene(30/70) Copolymer (Resin A-25)>

p-Hydroxystyrene (VP-8000, produced by Nippon Soda Co., Ltd.) in anamount of 70 g was dissolved in 320 g of propylene glycol monomethylether acetate (PGMEA) with heating, dehydrated by vacuum distillation,and then cooled to 25° C. To this solution, 0.35 g of pyridiniump-toluenesulfonate and 22.4 g of cyclohexane ethanol were added, andfurther 17.5 g of t-butyl vinyl ether was added at a slow speed. In theresulting mixture, reaction was run for 5 hours at 20° C. Thereafter,the reaction solution was admixed with 0.28 g of triethylamine and 320ml of ethyl acetate, and washed with 150 ml each of distilled water forthree times. Therefrom, the solvent was distilled away, and the residuewas concentrated. The thus obtained oil was dissolved in 100 ml ofacetone, and poured slowly into 2 liter of distilled water. As a result,a powdery matter separated out. This powdery matter was filtered off anddried to yield 54 g of the desired resin.

<(2) Synthesis ofp-(1-Cyclohexylethoxy)ethoxy)styrene/p-Acetoxystyrene/p-Hydroxystyrene(30/10/60) Copolymer (Resin A-38)>

p-Hydroxystyrene (VP-8000, produced by Nippon Soda Co., Ltd.) in anamount of 70 g was dissolved in 320 g of propylene glycol monomethylether acetate (PGMEA) with heating, dehydrated by vacuum distillation,and then cooled to 20° C. To this solution, 0.35 g of pyridiniump-toluenesulfonate and 22.4 g of cyclohexane ethanol were added, andfurther 17.5 g of t-butyl vinyl ether was added at a slow speed. In theresulting mixture, reaction was run for 5 hours at 20° C. Then, 5.53 gof pyridine was added to the reaction solution, and further thereto wasslowly added 5.9 g of acetic anhydride. Thereafter, the reactionsolution was admixed with 320 ml of ethyl acetate, and washed with 150ml each of distilled water for three times. Therefrom, the solvent wasdistilled away, and the residue was concentrated. The thus obtained oilwas dissolved in 100 ml of acetone, and poured slowly into 2 liter ofdistilled water. As a result, a powdery matter separated out. Thispowdery matter was filtered off and dried to yield 58 g of the desiredresin.

(3) The Following Resins were Synthesized in the Same Manner as inSyntheses (1) and (2).A-3: p-(1-Ethoxyethoxy)styrene/p-hydroxystyrene (35/65) copolymer(molecular weight: 15,000, dispersion degree (Mw/Mn): 1.1)A-7: p-(1-iso-Butoxyethoxy)styrene/p-hydroxystyrene (30/70) copolymer(molecular weight: 6,000, dispersion degree (Mw/Mn): 1.2)A-36: p-(1-Phenetyloxyethoxy)styrene/p-acetoxystyrene/p-hydroxys tyrene(30/10/60) copolymer (molecular weight: 11,000, dispersion degree(Mw/Mn): 1.2)A-41:p-(1-(4-t-butylcyclohexylcarboxyethoxy)ethoxystyrene/p-acetoxystyrene/p-hydroxystyrene(30/10/60) copolymer (molecular weight: 12,000, dispersion degree(Mw/Mn): 1.1)A-43:p-(1-Cyclohexylethoxy)ethoxy)styrene/p-t-butylstyrene/p-hydroxystyrene(30/8/62) copolymer (molecular weight: 18,000, dispersion degree(Mw/Mn): 2.3)A-22: p-(1-Benzyloxyethoxy)styrene/p-hydroxystyrene (25/75) copolymer(molecular weight: 13,000, dispersion degree: 1.3)A-35: p-(1-Benzyloxyethoxy)styrene/p-hydroxystyrene/p-acetoxysty rene(20/70/10) copolymer (molecular weight: 9,000, dispersion degree(Mw/Mn): 1.2)

Furthermore, the following resins as Component (B) was synthesized.

<(4) Synthesis of Resin A-48 as p-Hydroxystyrene/t-butyl acrylate(79/21) Copolymer>

In 150 g of dioxane, 84.1 g of p-vinylphenol and 22.4 g of t-butylacrylate were dissolved, and thereto a stream of nitrogen was introducedfor one hour.

Thereto, 6.91 g of dimethyl 2,2′-azobisisobutyrate was added, and theresulting mixture was heated up to 75° C. under a stream of nitrogen.Therein, polymerization was run for 12 hours. At the conclusion of thepolymerization, the reaction solution was cooled to room temperature,and diluted with 150 g of acetone. This admixture was added dropwise toa large amount of hexane to yield a solid polymer. The remainingmonomers were removed by repeating the dilution with acetone and thedropwise addition to hexane for three times.

The resulting polymer was dried at 60° C. under reduced pressure. Thus,the copolymer A-48 was obtained.

By NMR analysis, it was confirmed that the compositional ratio ofp-vinylphenol to t-butyl acrylate was 79:21.

And Mw of the resin obtained was 12,000 and the dispersion degree(Mw/Mn) thereof was 2.6.

<(5) Synthesis of Resin A-16 asp-(1-Isobutoxyethoxy)styrene/p-hydroxystyrene/t-butyl acrylate(20/59/21) Copolymer>

The copolymer (A-48) in an amount of 20 g was dissolved in 80 g ofpropylene glycol monoethyl ether acetate (PGMEA), and heated to 60° C.Then, this reaction system was decompressed gradually to 20 mmHg, andthe water and PGMEA in the system were removed by azeotropicdistillation. Thereafter, the system was cooled to 20° C., and thereto2.2 g of isobutyl vinyl ether and 3 mg of p-toluenesulfonic acid wereadded sequentially. After the addition was completed, the reaction wasrun for 2 hours, followed by neutralization of the acid with a smallamount of triethylamine. Then, ethyl acetate was poured into thereaction solution, and therefrom the salt was removed by washing withion-exchanged water. Further, the ethyl acetate and the water weredistilled away from the reaction solution under reduced pressure. Thus,the desired polymer A-16 was obtained.

<(6) Synthesis of Resin A-51 as p-Hydroxystyrene/styrene/t-butylacrylate (78/7/15) Copolymer>

Resin A-51 having molecular weight of 13,100 and a dispersion degree(Mw/Mn) of 2.7 was synthesized in the same manner as Resin A-48.

<(7) Synthesis of Resin A-49 asp-Hydroxystyrene/p-(t-butoxycarbonyloxy)styrene (60/40) Copolymer>

Poly(p-hydroxystyrene) having a weight average molecular weight of11,000 (VP-8000, produced by Nippon Soda Co., Ltd.) was dissolved in 40ml of pyridine, and thereto 1.28 g of di-t-butyl dicarbonate was addedwith stirring at room temperature. The admixture underwent reaction for3 hours at room temperature, and then poured into a solution constitutedof 1 liter of ion-exchanged water and 20 g of concentrated hydrochloricacid, thereby depositing a powdery matter. The powdery matter wasfiltered off, washed with water, and then dried to yieldp-hydroxystyrene/p-(t-butyloxycarbonyloxy)styrene (60/40) copolymer.

EXAMPLES 1 TO 30 AND COMPARATIVE EXAMPLES 1 TO 3

According to each of the formulations shown in Tables 1 and 2,ingredients were dissolved in a given solvent in their respectiveamounts to prepare a solution having a total solids concentration of 15weight %. This solution was filtered through a 0.1-μm polyethylenefilter to prepare a resist solution. The performance evaluations weremade on the thus prepared resist solutions in the following ways.

A: Evaluations by Exposure to KrF Excimer Laser

DUV42 (produced by Brewer Science Inc.) was coated on a silicon wafertreated with hexamethyldisilazane, and heated at 215° C. for 60 secondsto form an antireflective film having a thickness of 550 angstrom.

On the thus processed silicon wafer, each resist solution was coateduniformly by means of a spin coater, and dried by heating on a 120° C.hot plate for 90 seconds to form a 0.6 μm-thick resist film. The resistfilm was subjected to pattern exposure using a KrF excimer laser stepper(NA=0.63) and a mask pattern composed of lines and spaces. Immediatelyafter the exposure, the resist film was baked for 90 seconds on a 110°C. hot plate. The thus baked resist film was developed with a 2.38%aqueous solution of tetramethylammonium hydroxide at 23° C. for 60seconds, rinsed with purified water for 30 seconds, and then dried.

By use of the patterns thus formed on the silicon wafer, the followingperformance evaluations were made on each resist solution. The resultsobtained are shown in Table 3.

(Resolution)

The resolution is expressed in terms of the limiting resolution achievedunder the exposure required for reproducing a 0.18 μm line-and-space(1/1) mask pattern.

(Exposure Margin)

The exposure margin is defined as a value (%) obtained by dividing anexposure range reproducing the line widths of 0.16 μm±10% by an optimumexposure and expressing the quotient as a percentage, wherein theexposure required for reproducing a 0.16 μm line-and-space (1/1) maskpattern is taken as the optimum exposure. The greater the value, thesmaller change is caused in line width when a change in exposure occurs.

(Focus Depth)

The focus depth of 0.15 μm line-and-space is measured under the exposurerequired for reproducing the 0.15 μm line-and-space (1/1) mask pattern.The greater the measured value, the broader the focus depth.

TABLE 1 Acid Other generator component Surfactant Example (g) Resin (g)(g) Base (g) (0.02 g) Solvent 1 A-24 A-25 (10) — (1) W-2 PGMEA/ (0.4)(0.05) PGME (8/2) 2 A-25 A-38 (10) — (1) W-2 PGMEA/ (0.3) (0.05) PGME(8/2) 3 A-26 A-36 (10) — (2) W-2 PGMEA (0.5) (0.02) 4 A-27 A-43 (10) —(2) W-4 PGMEA (0.4) (0.02) 5 A-30 A-35 (10) — (3) W-4 EL/EEP (0.5)(0.05) 6 A-38 A-22 (10) — (3) W-4 BL (0.2) (0.01) 7 A-39 A-38 (5) D-2(1) (1) W-4 CH (0.3) A-3 (4) (0.02) 8 A-92/A- A-25 (7) — (4) W-2 PGMEA/28 (0.4) A-51 (3) (0.01) PGME (8/2) 9 A-1 A-38 (10) B′-1 (2) W-1 PGMEA(0.2) (0.1) (0.005) 10 A-24 A-38 (10) — (4) W-4 PGMEA/ (0.3) (0.05) PGME(8/2) PAG4-3 (0.1) PAG7-3 (0.5) 11 A-26 A-3 (10) — (5) W-3 PGMEA (0.3)(0.02) 12 A-1 A-51 (5) — (1) W-2 PGMEA/ (0.2) A-3 (5) (0.02) PGME (8/2)A-25 (0.2) 13 A-25 A-3 (2) D-2 (5) W-1 PGMEA/ (0.3) A-49 (1.5) (0.01)PGME (8/2) PAG7-5 (6.5) (0.1) 14 A-107 A-3 (8) B′-3 (1) W-4 PGMEA/ (0.5)A-48 (1) (0.1) (0.01) PGME (8/2) A-49 (1) (5) (0.01) 15 A-110 A-15 (10)— (4) W-2 PGMEA/ (0.3) (0.05) PGME (8/2) PAG4-32 (0.2) 16 A-97 A-1 (10)— (2) W-4 EL/EEP (0.3) (0.02) 17 A-24 A-48 (5) — (4) W-4 PGMEA/ (0.2)A-49 (5) (0.02) PGME (8/2) PAG4-3 (0.2) PAG7-3 (0.3) 18 A-92 A-48 (10) —(5) W-2 PGMEA (0.6) (0.02) 19 A-2 A-51 (10) — (1) W-3 PGMEA/ (0.4)(0.01) PGME (8/2) PAG4-4 (0.1) 20 A-3 A-49 (10) — (5) W-1 PGMEA (0.3)(0.02) 21 A-24 p-PHS (8) D-1 (2) (1) W-2 PGMEA/ (0.4) B′-2 (0.01) PGME(8/2) PAG4-36 (0.2) (5) (0.1) (0.02) 22 A-26 p-PHS/St (9) D-2 (1) (1)W-4 PGMEA (0.3) (0.01) PAG3-22 (2) (0.1) (0.01) 23 A-2 m-PHS D-3 (1) W-3EL/EEP (0.5) (8.5) (1.5) (0.02)

TABLE 2 Acid Other generator component Surfactant (g) Resin (g) (g) Base(g) (0.02 g) Solvent Example 24 A-19 A-48 (5) — (4) W-4 PGMEA/ (0.2)A-49 (5) (0.02) PGEM (8/2) PAG4-38 (0.2) 25 A-40 A-48 (10) — (5) W-2PGMEA/ (0.3) (0.02) PAG4-37 (0.1) 26 A-43 A-51 (10) — (1) W-3 PGMEA/(0.4) (0.01) PGME (8/2) 27 A-44 A-49 (10) — (5) W-1 PGMEA (0.3) (0.02)PAG4-3 (0.1) 28 A-48 p-PHS (8) D-1 (2) (1) W-2 PGMEA/ (0.3) B′-2 (0.01)PGME (8/2) PAG4-32 (0.2) (5) (0.2) (0.02) 29 A-51 p-PHS/St D-2 (1) (1)W-4 PGMEA (0.4) (9) (0.01) (2) (0.01) 30 A-49 m-PHS D-3 (1) W-3 EL/EEP(0.4) (8.5) (1.5) (0.02) PAG4-4 (0.1) Comparative Example  1 PAG-A A-25(10) — (1) W-2 PGMEA/ (0.4) (0.05) PGME (8/2)  2 PAG-A A-48 (5) (4) W-4PGMEA/ (0.2) A-49 (5) (0.02) PGME (8/2) PAG4-3 (0.2) PAG7-3 (0.3)  3PAG-B m-PHS D-3 (1) W-3 EL/EEP (0.5) (8.5) (1.5) (0.02)

(Explanation of Ingredients in Tables 1 and 2) Component (A)

-   -   PAG-A: Triphenylsulfonium perfluorobutanesulfonate    -   PAG-B: Bis(t-butylphenyl)iodonium perfluorobutane-sulfonate        Component (B) (amount mixed: value expressed on a solid basis)    -   p-PHS/St: Alkali-soluble p-Hydroxystyrene/styrene (85/15 by        mole) copolymer (weight average molecular weight: 20,000,        dispersion degree: 2.9)

B′-1 to B′-3 are the compounds having the following structural formulae,respectively:

D-1 to D-3 are the compounds having the following structural formulae,respectively:

Component (E) (Basic compound)

(1): 1,5-diazabicyclo[4.3.0]-5-nonene

(2): 2,4,5-Triphenylimidazole

(3): Tri-n-butylamine

(4): N-Hydroxyethylpiperidine

(5): Tetrabutylammonium hydroxide

Component (F) (Surfactant)

-   -   W-1: Megafac F176 (produced by Dai-Nippon Ink & Chemicals, Inc.)        (surfactant containing fluorine atoms)    -   W-2: Megafac R08 (produced by Dai-Nippon Ink & Chemicals, Inc.)        (surfactant containing both fluorine and silicon atoms)    -   W-3: Organosiloxane polymer KP-341 (produced by Shin-Etsu        Chemical Industry Co., Ltd.)    -   W-4: Troysol S-366 (produced by troy Chemical Industried, Inc.)        (surfactant containing fluorine atoms)

Solvent

-   -   PGMEA: Propylene glycol monomethyl ether acetate    -   PGME: Propylene glycol monomethyl ether (1-methoxy-2-propanol)    -   EL: Ethyl lactate    -   EEP: Ethyl ethoxypropionate    -   BL: γ-Butyrolactone    -   CH: Cyclohexanone

TABLE 3 Exposure Focus depth Resolution (μm) margin (%) (μm) Example 10.125 12.0 1.4 2 0.125 11.5 1.3 3 0.125 13.0 1.3 4 0.125 11.4 1.2 50.125 12.0 1.5 6 0.125 12.1 1.4 7 0.125 12.0 1.3 8 0.125 11.0 1.3 90.125 12.3 1.5 10 0.125 11.9 1.2 11 0.13 12.0 1.0 12 0.13 11.4 1.1 130.13 12.6 1.1 14 0.13 12.4 1.2 15 0.13 11.5 1.2 16 0.13 12.0 1.1 170.125 10.6 1.2 18 0.125 10.8 1.0 19 0.125 9.7 1.1 20 0.125 9.2 1.0 210.125 10.7 1.1 22 0.125 9.0 1.2 23 0.125 9.8 1.2 24 0.13 9.5 1.1 25 0.1310.1 1.2 26 0.13 9.4 1.1 27 0.13 10.5 1.2 28 0.13 9.0 1.0 29 0.13 9.71.2 30 0.13 10.2 1.1 Comparative Example 1 0.14 4.1 0.5 2 0.14 5.5 0.7 30.14 3.4 0.4

As can be seen from the data shown in Table 3, each of the resist filmsformed with the present positive resist compositions in Examples 1 to 30respectively achieved high resolution, and had a wide exposure marginand a broad focus depth in the pattern formation by exposure to KrFexcimer laser as a far ultraviolet ray.

In the cases of the resist films formed with the positive resistcompositions not containing the present Component (A) as in ComparativeExamples 1 to 3, on the other hand, both exposure margin and focus deptwere narrow.

Further, in the experiments for performance evaluations, no developmentresidues were detected on the present resist films formed in Examples 1to 30.

On the other hand, the resist films formed in Comparative Examples 1 to3 were unsuccessful in resolving patterns finer than 0.13 μm byoccurrence of development residue.

B: Evaluation by Irradiation with Electron Beams

Resist solutions were prepared according to the same formulations as inseveral (shown in Table 4) of Examples set forth in Tables 1 and 2,except that the total solid concentration was changed to 17%.

Additionally, 1 g of benzoyloxyvinyl ether (vinyloxyethyl benzoate) wasfurther added to each of the compositions in Examples 8, 13 and 23 andComparative Example 3.

Each of the resist solutions was coated uniformly on a silicon substratetreated with hexamethyldisilazane by means of a spin coater, and driedby heating on a 120° C. hot plate for 60 seconds to form a 0.8 μm-thickresist film. The resist film underwent irradiation with an electron-beamdrawing apparatus (acceleration voltage: 50 KeV, beam diameter: 0.20μm). Immediately after the irradiation, the resist film was baked for 90seconds on a 110° C. hot plate. The thus baked resist film was developedwith a 2.38% aqueous solution of tetramethylammonium hydroxide at 23° C.for 60 seconds, rinsed with purified water for 30 seconds, and thendried.

By use of the patterns thus formed on the silicon substrate, thefollowing performance evaluations were made on each resist. The resultsobtained are shown in Table 4.

(Image Evaluation)

The 0.2 μm contact hole patterns thus formed were observed under ascanning electron microscope and examined for their respective profiles.

(Sensitivity Evaluation)

The sensitivity was evaluated by the amount of irradiation (μC/cm²)required for reproducing 0.2 μm contact hole patterns.

(Resolution Evaluation)

The resolution was expressed in terms of the limiting resolutionachieved under the irradiation reproducing 0.2 μm contact hole patterns.

TABLE 4 Example (irradiation with electron Sensitivity Resolution beam)(μC/cm²) (μm) Profile  1 7 0.8 rectangular  8 5 0.8 rectangular 13 9 0.8rectangular 17 7 0.8 rectangular 21 7 0.8 rectangular 22 5 0.8rectangular 23 9 0.8 rectangular Comparative 8 0.9 somewhat Example 1inverted taper Comparative 7 0.9 somewhat Example 2 inverted taperComparative 7 0.9 somewhat Example 3 inverted taper

As can be seen from the results shown in Table 4, the presentcompositions achieved highly sensitive and highly resolved patternformation by electron-beam irradiation, and what is more, ensured arectangular profile in the resist patterns without providing an invertedtaper profile caused by a scattering phenomenon characteristic ofelectron-beam irradiation.

<Syntheses of Resins>

[Synthesis of Resin (P1), (a1)/(b1)=50/50]

A solution containing 5.0 g of 2-methyl-2-adamantane methacrylate, 4.23g of mevalonic lactone methacrylate and 0.534 g of a polymerizationinitiator, 2,2′-azobis(2,4-dimethylvaleronitrile) (V-65, produced byWako Pure Chemical Industries, Ltd.) in 30.0 g of N,N-dimethylacetamidewas added dropwise over a period of 4 hours to 7.0 g ofN,N-dimethylacetamide heated at 60° C. under a stream of nitrogen. Inthis admixture, the reaction was further continued for 2 hours at 60° C.Then, 0.267 g of V-65 was further added, and the reaction was run foradditional 2 hours. The reaction mixture was poured into 1,000 ml ofion-exchanged water, and the thus deposited powdery matter was filteredoff. The powdery matter was dissolved in THF, and poured into 1,500 mlof hexane. By drying the thus deposited powdery matter, the intendedResin (P1) was obtained.

The resin obtained had a weight average molecular weight of 5,500 and adispersion degree (Mw/Mn) of 1.9. Additionally, these values of weightaverage molecular weight and dispersion degree were measured by DSCmethod and expressed on a polystyrene basis.

[Syntheses of Resins (P2) to (P20)]

Resins (P2) to (P20) shown in Table 5 were each synthesized in similarmanner to the above. The molecular weights and dispersion degrees ofthese resins are shown in Table 5.

TABLE 5 Molecular weight (Dispersion Resin Monomers used (ratio) degree)(P1) a1/b1 (50/50)  5,500 (1.9) (P2) a1/b1/methacrylic acid (45/45/10) 9,000 (1.9) (P3) a4/b47 (55/45) 16,700 (1.8) (P4) a4/b5 (60/40)  4,600(2.2) (P5) a5/b47/methacrylic acid (45/45/10)  8,700 (2.1) (P6) a5/b1(50/50)  5,600 (1.7) (P7) a18/b1 (50/50) 23,000 (2.3) (P8) a16/b1(50/50) 12,300 (2.2) (P9) a16/b1/methacrylic acid (45/45/10) 14,100(1.9) (P10) b54/maleic anhydride (50/50)  3,600 (2.0) (P11)b54/b55/b56/maleic anhydride  5,400 (1.9) (15/25/10/50) (P12)a1/b1/diethylene glycol monomethyl ether 10,100 (2.4) methacrylate(47.5/47.5/5) (P13) b53/maleic anhydride/t-butyl acrylate 11,000 (1.8)(40/40/20) (P14) b53/maleic anhydride/t-butyl 13,000 (1.9) acrylate/a20(36/36/18/10) (P15) b1/b62/a5 (40/30/30) 11,000 (1.8) (P16) b53/maleicanhydride/b43/b42 11,000 (1.9) (30/30/30/10) (P17) b54/maleicanhydride/b48/b44 13,000 (2.1) (30/30/10/20) (P18) b53/maleicanhydride/b45 (35/35/30)  8,500 (1.7) (P19) b64/b63/a5 (40/30/30) 11,000(1.9) (P20) b64/b63/b65 (40/30/30) 13,000 (2.2)

<Resist Preparation> EXAMPLES 31 TO 71 AND COMPARATIVE EXAMPLES 4 TO 6

Resist solutions having a total solid concentration of 15% were eachprepared by dissolving ingredients shown in Tables 6 and 7, and filteredthrough a 0.1-μm Teflon filter. The thus prepared photosensitivecompositions were each evaluated by the following methods. The resultsobtained are shown in Table 8.

TABLE 6 Acid Other generator Resin component Surfactant Example (g) (g)(g) Base (g) (0.02 g) Solvent 31 A-24 (0.4) P1 (20) — (1) W-2 PGMEA/(0.05) PGME (8/2) 32 A-25 (0.3) P2 (20) — (1) W-2 PGMEA/ (0.05) PGME(8/2) 33 A-26 (0.5) P3 (20) — (2) W-2 PGMEA (0.02) 34 A-27 (0.4) P4 (20)— (2) W-4 PGMEA (0.02) 35 A-30 (0.5) P5 (20) — (3) W-4 EL/EEP (0.05) 36A-38 (0.2) P6 (20) — (3) W-4 BL (0.01) 37 A-39 (0.3) P7 (20) — (1) W-4CH (0.02) 38 A-92/A-28 P8 (20) — (4) W-2 PGMEA/ (0.4) (0.01) PGME (8/2)39 A-1 (0.2) P9 (20) B′-1 (2) W-1 PGMEA (0.1) (0.005) 40 A-24 (0.3) P10t-Bu (4) W-4 PGMEA/ PAG4-3 (18) cholate (0.05) PGME (8/2) (0.05) (2)PAG7-3 (0.5) 41 A-26 (0.3) P11 — (5) W-3 PGMEA (20) (0.02) 42 A-1 (0.2)P12 — (1) W-2 PGMEA/ A-25 (0.2) (20) (0.02) PGME (8/2) 43 A-25 (0.3) P13— (5) W-1 PGMEA/ PAG4-36 (20) (0.01) PGME (8/2) (0.1) 44 A-107 P14 B′-2(1) W-4 PGMEA/ (0.5) (20) (0.1) (0.01) PGME (8/2) (5) (0.01) 45 A-110 P1(20) — (4) W-2 PGMEA/ (0.3) (0.05) PGME (8/2) PAG4-32 (0.2) 46 A-97(0.3) P3 (20) — (2) W-4 EL/EEP (0.02) 47 A-24 (0.2) P10 — (4) W-4PGMEA/PGME PAG4-3 (20) (0.02) (8/2) (0.2) PAG7-3 (0.3) 48 A-92 (0.6) P11— (5) W-2 PGMEA (20) (0.02) 49 A-2 (0.4) P13 — (1) W-3 PGMEA/PGME PAG4-4(20) (0.01) (8/2) (0.1) 50 A-3 (0.3) P14 — (5) W-1 PGMEA (20) (0.02) 51A-55 (1) P15 — (1) W-2 PGMEA/PGME PAG4-5 (20) (0.05) (8/2) (0.2) 52 A-33(0.6) P15 — (1) W-2 PGMEA/PGME PAG4-4 (20) (0.05) (8/2) (0.1) 53 A-54(1) P14 — (2) W-2 PGMEA A-24 (0.2) (20) (0.02) 54 A-53 (1) P14 — (2) W-4PGMEA PAG4-38 (20) (0.02) (0.1)

TABLE 7 Other Acid generator Resin component Surfactant (g) (g) (g) Base(g) (0.02 g) Solvent Example 55 A-56 (0.2) P16 — (1) W-2 PGMEA/ Z31(0.4) (20) (0.05) PGME (8/2) 56 A-58 (0.3) P17 — (1) W-2 PGMEA/ Z21(0.5) (20) (0.05) PGME (8/2) 57 A-59 (0.4) P18 — (2) W-2 PGMEA Z22 (0.4)(20) (0.02) 58 A-60 (0.8) P19 — (2) W-4 PGMEA (20) (0.02) 59 A-62 (0.8)P20 — (3) W-4 EL/EEP Z13 (0.3) (20) (0.05) 60 A-66 (0.5) P16 — (3) W-4BL Z30 (0.4) (15) (0.01) P19 (5) 61 A-71 (0.5) P17 — (1) W-4 CH Z21(0.8) (20) (0.02) 62 A-72 (0.2) P18 — (4) W-2 PGMEA/ Z2 (0.2) (20)(0.01) PGME (8/2) Z1 (0.1) 63 A-76 (0.4) P17 (5) — (2) W-1 PGMEA Z6(0.2) P19 (0.005) (15) 64 A-66 (0.4) P16 (8) — (4) W-4 PGMEA/ Z31 (0.4)P20 (8) (0.01) PGME (8/2) Z21 (0.2) P6 (2) 65 A-80 (0.2) P19 — (2) W-4PGMEA Z31 (0.2) (20) (0.02) 66 A-81 (0.1) P20 — (3) W-4 EL/EEP Z21 (0.5)(20) (0.05) 67 A-84 P16 — (3) W-4 BL (0.15) z31 (15) (0.01) (0.2) P19(5) Z21 (0.3) 68 A-86 (0.4) P17 (1) W-4 CH Z13 (0.1) (20) (0.02) 69 A-87(0.5) P18 — (4) W-2 PGMEA/ Z14 (0.05) (20) (0.01) PGME (8/2) 70 A-90(0.7) P17 (5) — (2) W-1 PGMEA Z3 (0.1) P19 (0.005) (15) 71 A-80 (0.1)P16 (8) — (4) W-4 PGMEA/ A-91 (0.6) P20 (8) (0.01) PGME (8/2) P6 (2)Comparative Example  4 PAG-A P1 (20) — (1) W-2 PGMEA/ (0.4) (0.05) PGME(8/2)  5 PAG-A P10 t-Bu (4) W-4 PGMEA/ (0.3) (18) cholate (0.05) PGME(8/2) PAG4-3 (2) (0.05) PAG7-3 (0.5)  6 PAG-B P14 — (5) W-1 PGMEA (0.3)(20) (0.02)

(Explanation of Ingredients in Tables 6 and 7)

-   -   (1): 1,5-diazabicyclo[4.3.0]-5-nonene    -   (2): 2,4,5-Triphenylimidazole    -   (3): Tri-n-butylamine    -   (4): N-Hydroxyethylpiperidine    -   (5): Tetrabutylammonium hydroxide    -   W-1: Megafac F176 (produced by Dai-Nippon Ink & Chemicals, Inc.)        (surfactant containing fluorine atoms)    -   W-2: Megafac R08 (produced by Dai-Nippon Ink & Chemicals, Inc.)        (surfactant containing both fluorine and silicon atoms)    -   W-3: Organosiloxane polymer KP-341 (produced by Shin-Etsu        Chemical Industry Co., Ltd.)    -   W-4: Troysol S-366 (produced by troy Chemical Industried, Inc.)        (surfactant containing fluorine atoms)    -   PGMEA: Propylene glycol monomethyl ether acetate    -   PGME: Propylene glycol monomethyl ether    -   EL: Ethyl lactate    -   EEP: Ethyl ethoxypropionate    -   BL: y-Butyrolactone    -   CH: Cyclohexanone    -   PAG-A: Triphenylsulfonium perfluorobutanesulfonate    -   PAG-B: Bis(t-butylphenyl)iodonium perfluorobutane-sulfonate

<Image Evaluations> Sensitivity, Resolution, Exposure Margin and ScumEvaluations:

DUV-42 (produced by Brewer Science Inc.) was coated in a thickness of600 angstrom on a silicon substrate treated with hexamethyldisilazane,dried at 100° C. for 90 seconds, and further heated at 190° C. for 240seconds to form an antireflective film.

On the thus processed silicon substrate, each photosensitive resincomposition was coated by means of a spin coater, and dried by heatingat 120° C. for 90 seconds to form a 0.50 μm-thick resist film. Theresist film was subjected to pattern exposure using a ArF excimer laserstepper (NA=0.6, made by ISI Co., Ltd.) and a mask pattern. Immediatelyafter the exposure, the resist film was baked for 90 seconds on a 120°C. hot plate. The thus baked resist film was developed with a 2.38%aqueous solution of tetramethylammonium hydroxide at 23° C. for 60seconds, rinsed with purified water for 30 seconds, and then dried,thereby forming resist line patterns.

[Sensitivity]: The sensitivity is expressed in terms of the amount ofexposure required for reproducing a 0.16 μm mask pattern.

[Resolution]: The resolution is expressed in terms of the limitingresolution achieved under the amount of exposure required forreproducing a 0.16 μm mask pattern.

[Exposure Margin]: The exposure margin is defined as a value (%)obtained by dividing an exposure range reproducing the line widths of0.16 μm±10% by an optimum exposure and expressing the quotient as apercentage, wherein the exposure required for reproducing a 0.16 μmline-and-space (1/1) mask pattern is taken as the optimum exposure. Thegreater the value, the smaller change is caused in line width when achange in exposure occurs.

[Scum]: The following are evaluation criteria.

-   -   ◯; No scum was observed.    -   Δ; Scum was observed on patterns having line widths in the        vicinity of the limiting resolution.    -   X; Scum was observed on patterns having line widths wider than        the limiting resolution.

TABLE 8 Sensitivity Resolution Exposure Example (mJ/cm²) (μm) margin (%)Scum 31 7 0.11 10.0 ◯ 32 6 0.115 12.0 ◯ 33 8 0.12 11.5 ◯ 34 10 0.11510.4 ◯ 35 12 0.12 12.0 ◯ 36 8 0.12 11.0 ◯ 37 9 0.115 12.5 ◯ 38 10 0.1210.4 ◯ 39 7 0.115 11.0 ◯ 40 12 0.12 10.3 ◯ 41 12 0.12 10.0 ◯ 42 10 0.11510.5 ◯ 43 11 0.115 12.0 ◯ 44 8 0.115 11.4 ◯ 45 9 0.12 10.5 ◯ 46 10 0.1210.0 ◯ 47 7 0.115 12.2 ◯ 48 12 0.12 11.0 ◯ 49 11 0.115 10.9 ◯ 50 8 0.1210.0 ◯ 51 10 0.11 10.8 ◯ 52 5 0.11 12.0 ◯ 53 12 0.11 13.0 ◯ 54 9 0.1112.5 ◯ 55 9 0.11 12.3 ◯ 56 10 0.11 13.0 ◯ 57 12 0.11 12.2 ◯ 58 8 0.1113.1 ◯ 59 10 0.11 12.8 ◯ 60 7 0.11 13.5 ◯ 61 9 0.11 11.9 ◯ 62 11 0.1112.0 ◯ 63 12 0.11 13.3 ◯ 64 7 0.11 14.0 ◯ 65 12 0.11 12.5 ◯ 66 11 0.1113.1 ◯ 67 9 0.11 14.0 ◯ 68 10 0.11 13.3 ◯ 69 12 0.11 14.0 ◯ 70 12 0.1112.9 ◯ 71 10 0.11 13.0 ◯ Compar. Ex. 4 12 0.12 8.2 Δ Compar. Ex. 5 140.125 4.9 Δ Compar. Ex. 6 14 0.13 7.0 X

As can be seen from the results shown in Table 8, each of the resistfilms formed with the compositions prepared in Examples 31 to 71respectively had excellent sensitivity, resolution and exposure margin,and developed no scum.

On the other hand, each of the resist films formed with the compositionsprepared in Comparative Examples 4 to 6 respectively were inferior insensitivity, resolution, exposure margin or scum development to thosewith the compositions prepared in Examples.

In the lithography utilizing an exposure light source of shortwavelengths enabling superfine processing and positive chemicalamplification resist, the positive photosensitive compositions accordingto the present invention can achieve elevation of resolution, reductionof development residues, and improvements in processing latitudes, suchas exposure margin and focus depth.

Further, the present photosensitive compositions can deliver excellentperformances even in the case of using electron beams as energy beamsfor irradiation.

1-28. (canceled)
 29. A positive photosensitive composition comprising:(A) a compound capable of generating a sulfonic acid represented by thefollowing formula upon irradiation with one of an actinic ray andradiation; and (B) a resin which contains at least one of a monocyclicalicyclic structure and a polycyclic alicyclic structure and which iscapable of decomposing under the action of an acid to increase thesolubility in an alkali developer:

wherein m₁ is an integer of 0 to 3, A₁ represents a single bond, —O—,—CONR— or —COO, and R_(2a), R_(10a), R_(11a) and R_(13a) each representsa hydrogen atom, an alkyl group, a halo alkyl group, a halogen atom or ahydroxyl group.
 30. The positive photosensitive composition as claimedin claim 29, wherein m₁ is 0 or
 1. 31. The positive photosensitivecomposition as claimed in claim 29, wherein the resin (B) contains alactone structure.
 32. A pattern forming method comprising: forming aresist film with the positive photosensitive composition as claimed inclaim 29; exposing the resist film; and developing the resist film.